The longrunning series, which began as a 1992 film starring Kristy Swanson, is being re-imagined for a movie adaptation, with a new actress playing the cheerleader-turned-vampire hunter portrayed by Sarah Michelle Gellar on TV.
But Brendon, who played Xander Harris on the show, is worried the film will not find the same fanbase as the TV phenomenon gained.
He tells E! News, "I think it's a mistake. They have to reach a whole completely new fanbase, and we already have that fanbase. So it's going to really be hard to do that. But you know everyone - they remade The Flintstones. Twice, I think."
Brendon's former co-stars Alyson Hannigan, Michelle Trachtenberg and Anthony Head have all previously publicly condemned the planned remake, while creator Joss Whedon has also spoken out against the new movie.