Complete cast breakdown of NCIS season 23: Who plays who & where you’ve seen them before

NCIS season 23 brings together a mix of long-running favorites, returning agents, and new faces as the series enters its next major chapter. The new season picks up in the aftermath of Roman Parker’s shocking murder, placing Alden Parker and his team at the heart of a personal and dangerous investigation.

Leading the cast once again are established stars such as Sean Murray, Wilmer Valderrama, Katrina Law, Gary Cole, Brian Dietzen, Diona Reasonover, and Rocky Carroll, each reprising roles that have defined the show’s modern era.

The season also introduces Nancy Travis as Navy Vice Admiral Harriet Parker, expanding the series’ exploration of Parker’s past and family dynamics.

While Mark Harmon’s return as Leroy Jethro Gibbs remains unconfirmed, the ensemble is set to drive another year of high-stakes cases. Below is a complete breakdown of every major cast member and where you’ve seen them before.

All cast members of NCIS season 23

Sean Murray as Timothy McGee

Timothy McGee returns as the team’s senior Special Agent. Season 23 continues to show his steady leadership as Parker leans on him during the investigation into Roman’s murder. McGee remains the team’s calm center, balancing tech skills with field experience. Sean Murray has been with NCIS since season 1.

He is also known for roles in Harts of the West, JAG, and various film and TV projects earlier in his career.

Wilmer Valderrama as Nick Torres

Nick Torres enters season 23 more volatile after last season’s loss. His loyalty to the team and his instinct to go rogue drive several early plotlines. Torres’ emotional reaction to Parker’s crisis shapes the season’s tone.

Wilmer Valderrama joined NCIS in 2016 and is known for That ‘70s Show, voice work, and action-driven TV roles, making him a central force in the current ensemble.

Katrina Law as Jessica Knight

Jessica Knight continues as a key field agent, bringing tactical expertise and sharp instincts. Season 23 explores how far she will go to protect Parker, while her dynamic with Jimmy Palmer remains a quiet thread.

Katrina Law joined in season 18 and is known for Spartacus, Arrow, and procedural roles that highlight her action background and strong screen presence.

Gary Cole as Alden Parker

Alden Parker anchors season 23 as he confronts the murder of his father. His past, his “bad kid” history, and his complicated relationship with his sister fuel major story arcs.

Gary Cole took over team leadership in season 19 and brings decades of experience from The West Wing, Office Space, and a wide range of dramatic and comedic roles.

Brian Dietzen as Jimmy Palmer

Jimmy Palmer returns as the Chief Medical Examiner, providing key forensic insight into Roman Parker’s death. His steady compassion remains central to the team’s emotional balance.

Brian Dietzen has been with NCIS since season 1, evolving from Ducky’s assistant to a core cast member. He has also appeared in films like From Justin to Kelly and worked as a writer and producer on multiple NCIS episodes.

Diona Reasonover as Kasie Hines

Kasie Hines continues as the team’s forensic scientist, offering lab results that drive major breakthroughs in the season’s central investigation.

Her analytical style and grounded presence remain essential. Diona Reasonover joined in season 15 and is known for her comedic work on Clipped and appearances in projects like Grace and Frankie and Adam Ruins Everything.

Rocky Carroll as Leon Vance

Director Leon Vance returns to oversee the team during one of its most personal cases. His guidance shapes Parker’s pursuit of the truth, and his appearances continue to anchor NCIS leadership.

Rocky Carroll has played Vance since season 5 and has directed multiple episodes.

His career spans theater, film, and television, including notable roles in Chicago Hope and recurring characters on The Agency and Roc..

Nancy Travis as Harriet Parker

Nancy Travis debuts as Vice Admiral Harriet Parker, Alden Parker’s strict, accomplished sister. Her arrival deepens the exploration of Parker’s troubled childhood and introduces new tension as the siblings clash amid high-stakes operations.

Travis is known for Last Man Standing, Three Men and a Baby, and decades of film and TV roles.

Catch NCIS season 23 on CBS.