"I've been doing this professionally for 60 years," Nimoy told the Toronto Sun. "I love the idea of going out on a positive note. I've had a great, great time. ... I want to get off the stage. Also, I don't think it would be fair to Zachary Quinto. He's a terrific actor, he looks the part, and it's time to give him some space. And I'm very flattered the character will continue."
Nimoy originated the beloved character of Spock on the original "Star Trek" television series and reprised the role in numerous movies.
Quinto took over the part last year in the blockbuster film "Star Trek."
TVGuide.com said Nimoy started playing a recurring role on "Fringe" at the end of Season 1 after a 12-year hiatus from acting.
The show is now in its second season.