One said the "Entourage" star exposed himself and pinned her down on his bed in 1996.
"Wisdom of the Crowd" will end after just one season.
The extra says the incident happened in a dark hallway in 2009.
Advertising executive Tiffany Bacon said the actor exposed himself to her in a hotel, which Piven denies.
She hinted at a troubling experience with Piven when she was "far too young."