"I believe that certain things get left out, and when you make a film you're setting yourself up to disappoint people, Gellar told Zap2it.com.
"I say that now, and (in) a year someone could send me the script and I could think it's great ... But I will say that I have a lot of hesitations about it and it is not something I particularly want to do at this time," the 27-year-old actress said.
Gellar said leaving the series was one of the hardest things she's done.
"It was all I knew. I started that show when I was 18 years old. It was a character I loved. (The crew) were people I saw nine months a year for eight years of my life. It was incredibly difficult," Gellar said.
"Buffy's" final episode was broadcast May 2003 on UPN, where it aired after five years on the WB.