The 43-year-old actress starred in the Nineties fantasy hit from the age of 19.
A Buffy reboot has been in the works since 2018, with original showrunner Joss Whedon attached as an executive producer.
During an appearance on the On with Mario Lopez podcast, Gellar said: “I’m a wee bit, how do they say, long in the tooth for that.” She added that the monsters Buffy faced “were a metaphor for the horrors of adolescence”.
“I don’t think it’s me,” she said. “I don’t think I should be the one doing it… I’m way too tired and cranky to put in that work again.”
Gellar declined to discuss the abuse allegations that have been made against Whedon.
Last week, Charisma Carpenter – who portrayed Cordelia Chase on the hit series – accused Whedon of “abusing his power” on the set of Buffy, and claimed that he made “ongoing, passive-aggressive threats” against her.
Buffy actors Amber Benson (Tara) and Michelle Trachtenberg (Dawn) have since come forward with their own allegations against the writer-director.
Whedon has not yet responded to the allegations.
In an Instagram post, Gellar said: “While I am proud to have my name associated with Buffy Summers, I don’t want to be forever associated with the name Joss Whedon.”
The actor continued, saying she would not be making any further statements, and is currently “more focused on raising my family and surviving a pandemic.” She added, however, “I stand with all survivors of abuse and am proud of them for speaking out.”