The 55-year-old actor, who has played Gil Grissom for the past nine years, insisted that he is ready for a change.
"I won't miss Grissom. It was a complete life for me that's reached its end, and it's reached it in the right way, I think. So I won't miss Grissom. And I hope that the audience won't miss him either," he told Entertainment Weekly.
The star also revealed that he made the decision to exit the show after becoming too comfortable in his role.
"It's CSI - they pay me a lot of money, and I don't have to work very hard anymore. I've got it all figured out. And I just realised, God, as an artist, I'm going to atrophy. You do anything for nine years, it becomes somewhat rote.
"I didn't want to be on the show because they were paying me money and I liked the money. I didn't want to be on the show because it saved me from having to go look for other jobs. Just didn't want it. It was too safe for me at this point."