Several actors have declined roles or left NCIS under various circumstances, impacting the show’s dynamic over the years.​
Jon Bernthal, known for his role in The Walking Dead, was offered a role in NCIS: Los Angeles but turned it down to pursue his passion for the AMC series. He later reflected on the decision, acknowledging the significant time commitment of a network show like NCIS and expressing satisfaction with his choice to join The Walking Dead instead
Looper

Pauley Perrette, who portrayed Abby Sciuto, left NCIS in 2018 after 15 seasons. She cited workplace concerns, including an alleged incident involving Mark Harmon’s dog biting a crew member. Perrette expressed fear of Harmon and stated she would never return to the show due to these issues .​

Sasha Alexander, who played Caitlin Todd, departed after two seasons, citing the demanding schedule of network television. She felt that continuing would hinder her personal life and creative pursuits, leading to her decision to leave the series .​
Looper

These departures highlight the personal and professional challenges actors face in the television industry, influencing their decisions to leave or decline roles in long-running series like NCIS.​