Pauley Perrette left NCIS due to a combination of factors. While the exact reasons have not been explicitly disclosed by Perrette herself, reports suggest that issues related to workplace behavior and a toxic environment may have played a role in her decision to depart from the show. Perrette has since spoken out about experiencing “multiple physical assaults” and “traumatic events” while working on NCIS, although she did not specifically attribute her departure solely to these incidents. Ultimately, the specifics of Perrette’s departure remain largely undisclosed, but it appears to be a complex decision influenced by various factors.