A new era is beginning for NCIS as the series returns to the small screen with a new cast of actors and characters for 2024's Season 21.
First brought to life in 2003 as a spin-off of JAG under creators Donald Bellisario and Don Gill, NCIS now holds a place as the longest-running series in the franchise.
The writer's room for Season 21 officially opened in October 2023, although this season marks the first without any of the actors who starred in the Season 1 pilot.
Every Main Actor and Character in NCIS Season 21
Sean Murray - Timothy McGee
Sean Murray first joined NCIS in Season 1's seventh episode, and he is now the longest-running member of the show's cast as Senior Field Agent Timothy McGee.
Known for his intellect and myriad of skills, Special Agent McGee took over Tony DiNozzo's (Michael Weatherly) position in Season 13, now serving as second-in-command for the Major Case Response Team.
NCIS is Murray's biggest credit, appearing in over 440 episodes to date. He is also known for his memorable cameo as Thackery Binks in 1993's Hocus Pocus along with credits in This Boy's Life and Harts of the West.
Wilmer Valderrama - Nick Torres
Special Agent Nicholas "Nick" Torres made his NCIS debut in Season 14 via a performance by Wilmer Valderrama, with the character coming in as a former undercover agent who joins the team after avenging his sister's death.
Boasting proficient skills in combat and marksmanship, Torres is known to be quite unpredictable in the field. He has trouble at first readjusting to being part of a team even though he's quite charismatic and funny, and he is often superstitious about anything tied back to the dead.
Along with recent crossover appearances as Torres in NCIS: Los Angeles and NCIS: Hawai'i, Valderrama is most recognizable for his eight years of work as Fez in That '70s Show. Other credits include Encanto and Larry Crowne.
Katrina Law - Jessica Knight
Katrina Law took her place in the NCIS cast during Season 18 playing the role of Jessica Knight, a special agent who took Ellie Bishop's (Emily Wickersham) place on the main team.
First joining after working a case to catch someone who bombed and killed one of her former teammates, Knight plays no games with her no-nonsense attitude and often keeps the team in line as they work cases.
Law is recognizable for her portrayal of Nyssa al Ghul in The CW's Arrowverse, appearing in Arrow and the Legends of Tomorrow crossover series. She is also seen in the Training Day TV series, Spartacus, and Apparition.
Brian Dietzen - Dr. Jimmy Palmer
Brian Dietzen is one of only two main NCIS cast members who go back to Season 1, having played Jimmy Palmer since that season's last three episodes before becoming a series regular in Season 10.
Palmer revealed in Season 14 that he had become a qualified medical examiner, taking on more responsibility with the team.
However, Season 21 will be trying for Dr. Palmer after the death of original series star David McCallum (who played Palmer's former boss Dr. Donald "Ducky" Mallard) in 2023 on top of losing his wife Breena in Season 18.
Dietzen can also be seen in From Justin to Kelly, Congratulations, and Karaoke Man.
Diona Reasonover - Kasie Hines
Kasie Hines serves as the NCIS team's forensic specialist after Diana Reasonover joined the series in Season 15, replacing Pauley Perrette's Abby Sciuto following her departure at the end of Season 15.
Season 16 saw Hines permanently replace Sciuto, and she's known for her warm demeanor and her penchant for joking around and making her teammates laugh.
Reasonover boasts credits in Grace and Frankie, Drive Share, 2 Broke Girls, and Superstore.
Rocky Carroll - Leon Vance
Rocky Carroll first embodied the character Leon Vance in Season 5 of NCIS, with the character being named NCIS Director after former director Jenny Shepard's (Lauren Holly) death in the Season 5 finale.
While fans were worried about a potential exit for Vance during Season 19, the character remains firmly entrenched in the story as he continues to lead the agency through difficult challenges.
After losing his wife in Season 10 and going through intense torture in Season 15, Season 19 saw him become the victim of a home invasion, although he got back on his feet quickly thereafter.
Other major credits for Carroll include Chicago Hope, Yes Man, and Born on the Fourth of July.
Gary Cole - Alden Parker
Gary Cole became the newest member of the NCIS cast in Season 19, Episode 2, playing former FBI Special Agent Alden Parker.
Parker was sent to Alaska to arrest former NCIS Supervisory Agent Leroy Jethro Gibbs (Mark Harmon), but after he let Gibbs go, Gibbs recommended Parker to take over his position as Harmon left the series.
Cole is known for his work in Talladega Nights: The Ballad of Ricky Bobby, Dodgeball: A True Underdog Story, and Office Space. He's also heard in voiceover roles in Family Guy and Kim Possible.
New episodes of NCIS Season 21 air on Monday nights at 9 p.m. ET on CBS before streaming on Paramount+.