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."
Piven says he "unequivocally" denies the allegations.
Jeremy Piven joined HuffPost Live on Tuesday to discuss one of his hardest auditions when a casting director called him out
Jeremy Piven discusses being called out for a "batsh*t" audition.
Jeremy Piven discusses the fourth and final season of "Mr Selfridge."
Actor Jeremy Piven swings by HuffPost Live to talk shopping, style, and that 'stache from his hit show "Mr. Selfridge."
Déjà Vu: Chatting With Giorgio Moroder and Doraemon's Yoshihiko Shinoda, Plus Hy Brasil, Adham Shaikh, Owl and Old Man Luedecke Exclusives
When you look at current technologies, are there moments for you as a producer when you look back at your earlier records with Donna Summer, Blondie or David Bowie and others and say, "I wish we'd had this technology back then"?
This expansion of the HBO TV series appears to have been conceived by a gaggle of misogynistic, beer-chugging adolescent virgins who brag about getting laid, but the closest they've ever gotten is a Playboy centerfold.