Grisha Alexandrovich Nikolaev
Alias: G. Callen; ("G."; or "Callen" to his NCIS colleagues)
Gender: Male   Male
Status: Alive
  Occupation Affiliation Rank / Title
 ●   Federal Agent   NCIS   Special Agent
            ●     NCIS: OSP       Field Agent
 ●   Federal Agent   DEA   Special Agent
 ●   Federal Agent   CIA   Special Agent
 ●   Federal Agent   FBI   Special Agent
Portrayed by: Chris O'Donnell
Kyle Michael Dietz- (young G. Callen in flashbacks in "Pushback").
Charlie O'Donnell- (young Callen in "Callen, G.").
Finley O'Donnell- (young Callen in a flashback in "Tin Soldiers").
C.J. Valleroy-(Callen aged fifteen/teenage Callen in flashbacks in "Rage").
 First Appearance
  ●   NCIS: Legend Part 1 (episode)
  ●   NCIS: LA: Identity (episode)
 Last Appearance
  ●   NCIS: Legend Part 2 (episode)
  ●   NCIS: LA: n/a- main character
List of Appearances

Grisha Alexandrovich Nikolaev or G. Callen (G. or Callen to his NCIS colleagues) is an NCIS Special Agent and also a member of the Office of Special Projects in Los Angeles as well as the lead agent of the OSP field team.



Callen was born in Romania on March 11, 1970 to a Russian father, KGB Major Nikita Alexsandr Reznikov and Clara Callen, a half-Roma CIA agent. He had an older sister named Amy.

Clara's father had killed many members of the Comescu family, which led to a bloody feud between the two families. In retaliation, the Comescu family killed Callen's grandfather, George Callen, and Clara attempted to flee to the U.S with her two children.

Unfortunately, the Comescus still held a strong, undying grudge against the Callens, and two assassins working for the Comescu family killed Clara while they were awaiting the arrival of Henrietta Lange at a beach. Hetty, at that time an officer with the CIA, had been Clara's handler. She had been dispatched to help Clara and her children, but she arrived too late. The second assassin distracted young Grisha Callen by giving him a toy soldier.

The trauma associated with these events resulted in young Callen suppressing the memories from his subconscious for many years.

Callen and his sister, Amy, were brought to the U.S. by Hetty after the death of their mother and were placed in separate orphanages. In 1975, at the age of five, Callen was removed from the orphanage where he had originally been placed and was transferred to the foster care system run by the State of California. His older sister Amy remained in the orphanage where she had been placed.

During the thirteen years he was a ward of the State of California, Callen was placed in over thirty-seven foster homes. He presumably experienced various problems in the foster homes he was in, which in turn left him emotionally damaged and unable to trust anyone whatsoever.

While Callen was a teenager, he would continuously get in trouble. Hetty Lange "rescued" him and took him under her wing. She worked with and trained Callen.

Upon turning eighteen, Callen enlisted in the United States Army although his history and what rank he held remain unknown.

Following his military service, Callen became a federal law enforcement officer serving at various times with the Central Intelligence Agency (CIA), the Drug Enforcement Agency (DEA), and the Federal Bureau of Investigation (FBI) prior to joining NCIS.

NCIS Season 6

Callen made his debut appearance in the NCIS Season 6/NCIS: Los Angeles backdoor pilot episode, "Legend Part 1". He was introduced ignoring a call from his boss, NCIS Special Agent Lara Macy before he spoke to his old friend, fellow NCIS Special Agent Leroy Jethro Gibbs.

The two spoke for a while about the past they had shared together although they were interrupted by a young Russian woman cycling by.

After they had finished, Callen left to go get ready for the second undercover operation he would play a main role in. Following the successful conclusion of the case Callen was critically wounded in a drive by shooting.

NCIS: Los Angeles Season 1

Callen appeared in the NCIS: Los Angeles Season 1 premiere episode, "Identity" where he was first seen in a small room, presumably at a B&B, remembering the near-fatal shooting. It was shown that he had been left with permanent scars on his back as a result of being shot four months earlier.

After that, Callen packed up his belongings and headed for the beach where he got two coffees. Some time later, Callen's partner, NCIS Special Agent Sam Hanna. He arrived with the two men, wondering if Callen was ready to come back with Callen insisting he was. When Sam questioned him on why he'd left his latest area, Callen had said that it was too noisy, revealing that he had a habit of moving around due to the fact that the accommodation he lived in was not suited to him. The two then grabbed Callen's respective belongings and left but not before Sam told Callen that the new building they now worked in was "noisy". A while later, the Dodge Challenger arrived at an abandoned building with Callen later being left stunned at the fact that the Office of Special Projects worked inside a building that had been condemned following the Northridge Earthquake in 1994.

In the first season episode entitled "Pushback" Callen and the team learned that the attempted murder of Callen had been orchestrated by a former CIA operative named Ethan Stanhope. Stanhope desired to eliminate all persons with knowledge of Operation Cossack, a joint NCIS/CIA operation in Russia that failed when it was compromised by Stanhope. Stanhope's goal was to conceal his treasonous actions and prevent any adverse disclosures that would have harmed his business ventures. Despite Stanhope's best efforts, Callen, backed by Sam and Kensi, succeeded in arresting Stanhope, finally closing the case for good.

NCIS: Los Angeles Season 2

Callen's investigations into his family's history force Hetty to take drastic measures to protect Callen from the Comescus. Hetty resigns from NCIS and travels to Romania. Posing a member of the Comescu family she attempts to shield Callen from them by presenting the head of the family with a false death certificate in the second season finale entitled "Familia."

NCIS: Los Angeles Season 3

The premiere episode of the third season entitled "Lange, H." Hetty's plans go awry when Callen's team attempted to effect a rescue; resulting in the death of Alexa Comescu, the head of the Comescu family and the wounding of Hetty.

In a subsequent crossover event involving NCIS: Los Angeles and Hawaii Five-0, Callen traveled to Hawaii with Sam after learning that Dracul Comescu, the senior surviving member and current head of the Comescu family and was now on the NCIS: Los Angeles's Most Wanted list, had been sighted there.

NCIS: Los Angeles Season 4

For much of the fourth season Callen is focused on building a case against Marcel Janvier,

NCIS: Los Angeles Season 5

In the 100th episode of NCIS: Los Angeles, titled "Reznikov, N." a man pretending to be his father (Michael Reinhardt) was kidnapped. A message was left at the scene: "Callen we have your father." Throughout the episode, many pictures of Callen from when he was younger were shown. One of the pictures sparked an old memory. In a conversation with Kensi and Deeks, Callen revealed that he used to garden with one of his foster mothers, but his foster father used to beat him over the head with a broom handle. He revealed that he was moved from the foster home not because of the father's abuse, but because one day Callen took the broom handle from him and broke it over his foster father's head. It was revealed at the end of the episode that Michael was not truly Callen's father, but Callen learned his father's name: Nikita Alexander Reznikov.

NCIS: Los Angeles Season 6

NCIS: Los Angeles Season 7

In Angels and Daemons (episode), Callen was revealed to be keeping an eye on Joelle given how the OSP team had had their identities leaked last year.

He and Sam also got into an argument over the fact that they had agreed to carpool to work but that Callen had failed to give Sam any notice of arriving to work early.

Callen along with the rest of the Office of Special Projects team later gathered in Ops to discuss the team's latest case: the murder of former Navy Lieutenant Larry Overson who had founded the anti-virus company, "OverGuard". Callen and Sam head out to investigate the last suspected sighting of Overson's former best friend, former Navy Lieutenant Mark Powell.

The two arrived at the area in Winchester and searched Powell's car but discovered that the trunk was a mess, much to Callen's own personal disgust, causing him to comment that it resembled Kensi's desk.

They both soon discovered that Powell had fled with his belongings, leaving a smashed cell phone with the SIM card having been removed.

Callen contacted Eric and Nell for further information. They revealed that security footage taken from the marina showed that Powell had been in the area at the same time that Overson had been murdered, resulting in Powell becoming the first official suspect in the murder investigation.

Callen and Sam later arrived in Ops and learnt from Eric and Nell that Powell had taken a bus and would arrive at the metro station, leading to both NCIS Agents suspecting that Powell could flee to San Diego and then Mexico.

A while later, Callen and Sam headed to the bus stop where Powell was. Callen intercepted Powell with Sam later providing back-up but Powell attempted to flee by throwing his duffel bag at Sam who caught it.

Despite Powell's efforts, Callen caught up to him and arrested him, Callen noting the bruise on the left side of Powell's face with him insisting that he wasn't saying anything without his lawyer.

In the main area of the Boatshed, Callen and Sam yet again discussed Joelle but the discussion was interrupted by Wilson Rowe, Powell's lawyer informing the two NCIS agents that they were ready.

In Interrogation, Callen and Sam attempted to learn more information, only for Rowe to stonewall Powell. When Powell insisted that he wanted to come clean regardless of the punishment, Rowe stated that he couldn't be Powell's lawyer anymore and left.

With Rowe gone, Powell informed Callen and Sam of the daemon he and Overson had created during their time at the NSA with Callen voicing his belief that the two men had violated the Espionage Act. Powell stated that that was why he was running; because he had thought Overson had turned him in.

Powell also stated that he and Overson had met and fought but that he hadn't killed him.

Once the Interrogation had finished, Callen and Sam met with Granger to discuss the daemon and the possibility that foreign intelligence agencies had been attempting to infiltrate American tech companies for years.

Later, in Ops, Callen, Sam, Kensi, Deeks and Nell gathered to compare notes on the case with Nell revealing that Vincent Lee, the new security guard for Flibbit barely existed.

Callen then asked Kensi and Deeks to go interrogate Powell about Rowe and then informed Sam that they needed to go undercover at Flibbit.

Despite Eric volunteering, Hetty agreed with Nell, instead choosing Callen and Sam and informing the two to be prepared to make the fastest billion in history.

Later, Callen posing as "Curtis Williams" headed to Flibbit where he and Sam who was "Samuel Wright" met the programmers including Austin Chopra.

The two later met Jessica Moore and discussed how they could help Flibbit.

Once the meeting had ended, Callen headed off with Chopra with Callen taking the slide down to the bottom level of Flibbit and stating that he'd beaten Chopra.

Callen later spoke with Chopra and discussed the code while Eric told Callen via an earpiece that he'd have to dig a little deeper as Chopra was only showing them the bare minimum.

Once that had ended, Callen and Sam left.

In the Bullpen, the team gathered and learnt that Chopra and Batool Shah were both agents for the ISI, the Pakistan Intelligence Service agency, and that Batool was presumably responsible for killing Rowe. The team was left stunned when they learnt that the daemon had started uploading to users phones and that Flibbit's users were composed of senators, CEOs, and even active members of the United States military.

Later, now wearing NCIS bulletproof vests and carrying guns, Callen, Sam, Kensi and Deeks crept into Flibbit Headquarters. After an intense gunfight, they saved Mossad officer, Noam Haber. Haber had been posing as the security guard, Vincent Lee. The team killed Chopra and Shah, as well as the third ISI agent: Miles.

Eventually, in the bullpen, Callen and Sam discussed Joelle once again with Callen admitting that he did have some regrets over breaking up with Joelle. He and Sam later left the bullpen, the two engaging in a good old fashioned argument.

NCIS: Los Angeles Season 8

Callen learned that his father, now living in the United States had another relationship following his separation from Clara, and that he has a daughter name Alexandra.

NCIS: Los Angeles Season 9

NCIS: Los Angeles Season 10


Callen is very conscientious when it comes to work. As the lead field agent in charge, Callen is somewhat strict at times, such as when Deeks was unsure about returning to the field following a traumatic experience. Callen told Deeks he did not want him back until he was sure. By then, Deeks had firmly decided to return, which Callen then let him do. In addition, he stays on top of what is going on with his team members, often being quick to pick up on when something is wrong, or happening in their lives. He also has been known to (somewhat randomly) check up on them at times. Further, he is usually one of the first members to get up and respond when Eric and/or Hetty tell the team that they have a new case. Callen is also very determined to solve the cases, in that he does not hesitate to send the team into dangerous undercover missions.

However, Callen also has a light side. He has strong sense of humor, like the rest of the members on the team. He frequently jokes in times when the team members are sitting and waiting for something to happen or when going undercover. He also jokes around during quieter moments, in between cases. His sense of humor makes his colleagues like to work with him. He is also somewhat of a ladies man that he has had a few different girlfriends. Despite having gone through a few in a relatively short time period, he is usually faithful, and most of his relationships have ended as a result of the girlfriends betraying him. This causes him to sometimes hold back and recover before getting into a new relationship, showing that he really does take his relationships seriously, caring about making them work.

Relationship with Colleagues

Sam Hanna

Callen and Sam are partners within the Office of Special Projects branch of NCIS. They share a stereotypical, comical "Buddy Cop" relationship that can sometimes be interpreted as brotherly. Sam is one of the handful of people that Callen trusts, evidenced by both being able to pick up on each other's quirks and bad habits. They have excellent teamwork in the field and are very loyal to one another. Despite this, Sam still has a desire to learn more about Callen's mysterious past.

Leroy Jethro Gibbs

Callen and Gibbs served together at least twice--first in Serbia and then in Moscow. It hasn't been stated exactly when, how, or where they met, though Callen does say that Gibbs saved his life "that first time" in Serbia. Callen has an intimate knowledge of Gibbs' past, as he is aware of Gibbs' boat-building hobby and his three failed marriages. It is interesting that in NCIS episode Legend Part 1, Gibbs corrects and freely reveals to Callen that he had been married four times, indicating that Gibbs by now trusts Callen with this information. By his own admission Callen considers both Macy and Gibbs family. Callen is one of the few people that Gibbs permits to call him "Jethro."

Henrietta Lange

Callen's relationship with Hetty is one of mutual respect and trust. Conversely, although Hetty's position as operations manager requires her to run a tight ship, she at times lets down her guard and adopts a motherly attitude towards Callen. This motherly attitude is demonstrated at the conclusion of Identity when she covered the sleeping Callen with a blanket before she departed for the night. In the later seasons, it is revealed that Hetty is the one that got Callen out of the Orphanage and into foster care. She was his mother's CIA handler. It is also revealed that Hetty knows more about Callen than she lets on.

Tracy Rosetti

Callen's relationship with Tracy is strained because, although he respects her commitment to the mission, he is still angry that she chose her career over their Partnership. His anger stems from feelings of abandonment because while on a mission, the conditions deteriorated and Callen was detained by local authorities. Rather than compromise the mission by attempting to extricate Callen from his difficult situation, she retreated to a safe house maintained by the Agency.

At one point, Callen and Tracy married to maintain their undercover aliases. Callen revealed in a light-hearted manner that in the divorce settlement, Tracy got their dog, Buddy, and his name was Callen's safe word for an undercover operation after Tracy took a building full of naval sailors and civilians hostage.

Kensi Blye

Callen's relationship with Kensi is one seen between siblings. Callen treats Kensi as a little sister. He goes out of his way to protect and care for her. Kensi knows that Callen will always have her back and will protect her. Callen frequenty acts like an over-protective older brother.

Although there were hints of the pairing in the first season, the producers obviously chose to pair her with Deeks, so she and Callen were back to the brother/sister like relationship. There have been a few times when Callen and Kensi have gone undercover as a couple, and they have great chemistry with each other. However, neither of them see the other in a romantic way.

Callen and Kensi are the typical siblings, anybody would wish for. They are protective of each other, tease each other frequently, can be serious if the situation requires it, but most of all: they will always be there for each other and have each others back.

Marty Deeks

The relationship between these two is sort of a tease and torment. Mostly from Callen to Deeks. This is partly because of the difference between them (cop vs. federal agent) and the fact that Marty is just so tease-able. However, both of them know that it is only play and in reality they are part of a team and will always look out for one another and have each other's back. Callen was also the most accepting of Deeks (from the team) when he first became LAPD's liaison.

Nell Jones

Nell and Callen have a close, friendly relationship with each other. There have been many moments when the chemistry between the two has been seen as flirtatious and even romantic, although nothing ever comes of it. Nell is also Callen's ear for many things. Even when Hetty refuses to give Callen information regarding certain situations and cases, Nell often tells Callen anyways.

Self-defense kills


  • Between the ages of 5 and 18, Callen lived with a total of 37 foster families.
  • He didn't shoot a gun for the first time until he was 20 years old.
  • He can't stand needles.
  • He speaks a multitude of languages, including (but as far as we know, not limited to) French, German, Russian, Romanian,Herbrew, Turkish, Polish and Chechen.
  • Has been seen driving an Aston Martin in recent episodes of the show.
  • He is a New England Patriots Fan.
  • Callen's cars over the years have varied, from a silver Aston Martin Rapide to various Mercedes Benz, and even a couple of Jaguars. His first one was a standard Jaguar XKR. He then upgraded to the more powerful XKR-S
  • Had started dating Joelle Taylor in War Cries (5x14) after a blind date set up by Sam and Michelle Hanna But they broke up in Cancel Christmas (7x11).
  • Sam's daughter Cam calls him Uncle Callen
  • Despite Callen's real name finally revealed, he still primarily referred to as 'G' or 'Callen' because his full name was too long or too difficult to read.
    • Callen's first name, "Grisha", is a diminutive of "Gregory"
    • Callen's father is the only character to refer to him primarily as "Grisha".
  • In many flashbacks to Callen's childhood, Lily, Charlie and Finley O'Donnell (Chris O'Donnell's children) played a young Amy and G. Callen.
  • Callen volunteered as a wildlife firefighter when he was eighteen.


Callen: What are we, if anyone asks?

Sam: Uhh, city inspectors?
Callen: No, no one talks to city inspectors.
Sam: Okay, you're a realtor, and I'm your client. You're showing me an apartment.
Callen: Do I look like a realtor?
Sam: Okay, I'm a realtor, and you're the guy looking for an apartment. Can we go?
Callen: Would I live in a place like this? I don't even know if I can afford a place like this.
Sam: That's why I'm showing you, to see if you'd wanna live in a place like this.
Callen: Does it have a Jacuzzi?
Sam: If it has, I'm going to drown you in it.