Like his good friend and fellow NCIS Special Agent Leroy Jethro Gibbs who runs the Major Case Response Team in Washington D.C, Callen is also the lead Agent of the Office of Special Projects with his partner in the field being former Navy SEAL, NCIS Special Agent Sam Hanna.
Born in Romania to an unnamed father and Clara Callen, a CIA agent, young G. Callen lived a relatively normal life up until the age of six or seven.
The Comescu family who Callen's grandfather and possibly Clara's father had killed many members of later retaliated by killing Callen's grandparents before their daughter, Clara escape to the United States. Unfortunately, the Comescus still held a strong, undying grudge against the Callens and an assassin working for the family later killed Clara while another man distracted young Callen by giving him a toy solider.
At some point, young G. Callen and his sister, Amy were brought to the United States with both children being placed in foster homes. Amy died when she was very young while Callen grew up as part of the foster system.
Upon turning eighteen, Callen presumably joined the Army while working for the CIA in his later years. He then joined NCIS where he had assignments which had him working with Gibbs with the tasks bringing both men to Serbia and Russia with Gibbs saving Callen's life on both occasions in the two countries.
At some point, Callen was reassigned to the Office of Special Projects where he remains to this day.
NCIS Season 6
Callen was first seen talking to Gibbs in a small park located presumably on Venice Beach with the two agents remembering the times they'd spent together in the past.
In Legend Part 2 (episode), Callen went undercover as arms dealer, Liam Coyle and was able to infiltrate the main terrorist cell which was located in a car shop in downtown Los Angeles.
A few hours later and after the case had been solved, Callen was left badly wounded in a surprise drive-by shooting that Sam also witnessed.
NCIS: Los Angeles Season 1
Four months later Callen returned to his duties where it was later revealed that a former CIA operative Ethan Stanhope arranged the assassination attempt. 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.
NCIS: Los Angeles Season 2
NCIS: Los Angeles Season 3
In Episode:Pa Make Loa (Hawaii Five-0), a crossover with NCIS: Los Angeles and also a part of Hawaii Five-0 Season 2, Callen traveled to Hawaii with Sam after learning that Callen's sworn enemy, Dracul Comescu and who was now on the NCIS: Los Angeles's Most Wanted list had been sighted in Hawaii.
NCIS: Los Angeles Season 4
NCIS: Los Angeles Season 5
NCIS: Los Angeles Season 6
Relationship with Colleagues
Callen and Sam are partners within the Office of Special Projects branch of NCIS, they share a stereotypical always 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 and 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 and 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 Gibbs, in NCIS episode Legend Part 1, 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 in Legend Part 1, Callen considers both Macy and Gibbs family. Callen is one of the few people that Gibbs permits to call him "Jethro."
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.
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 marriage. 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.
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.
The relationship between these to 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.
- Callen is played by Chris O'Donnell who viewers may recognize from his role as Robin in "Batman and Robin" and "Batman Forever".
- In the first two seasons of NCIS: Los Angeles, Callen and his colleagues with the exception of Detective Marty Deeks carried a SIG-Sauer P228, the current weapon of choice for their Washington D.C counterparts, the Major Case Response Team led by Leroy Jethro Gibbs. At the beginning of Season 3, however, they switched to the new model SIG-Sauer P229 with the redesigned slide and new grips which they have continued to carry to this day.
- With the exception of JAG, Callen is the only NCIS: Los Angeles character along with Sam Hanna and Kensi Blye to have appeared on NCIS and Hawaii Five-0.
- NCIS: (6 season; 3 episodes; First appearance)
- NCIS: Los Angeles (See G. Callen on the NCIS: Los Angeles Database for more details)
- Hawaii Five-0: Episode:Pa Make Loa (Hawaii Five-0)