The 66-year-old actor also revealed how the show will 'adjust' to the major exit.
NCIS will give Pauley Perrette a proper departure.
ET's Kevin Frazier spoke with Mark Harmon at his TV Guide cover party in Studio City, California, on Monday, where he opened up about how the show will say goodbye to one of its own when Perrette leaves after season 15.
According to the 66-year-old actor, the fans have also earned a sweet departure for Perrette's Abby Sciuto. The actress revealed last month that this season would be her last.
"Oh, we'll miss her. I'm really aware, and we're all aware that audiences grow to love characters, and it's a big deal. And we honor that," Harmon said. "Fifteen years is a long time. People do what they do, and they move on and they do other things and that's part of life."
"It's given us, as a show, an opportunity to rebirth, to rejuvenate, to try new things, to grow," he added. "We adjust."
Harmon's TV Guide cover hits newsstands on Thursday, and NCIS airs Tuesdays on CBS.
See more on Perrette's exit in the video below.