The Spring Breakers star has previously admitted making a saucy bedroom film when he was a young man, and he has now confirmed the other participant was former The Practice star Sokoloff.
Franco dated Sokoloff for four years after they made 2000 movie Whatever It Takes together, and he insists their sex tape wasn't "made for public consumption."
He tells radio host Howard Stern, "It was with my girlfriend... She's an actress. She's married now... I'll say (her name) because it wasn't anything bad, it was an innocent thing we made for ourselves... And everybody knows."
"I dated an actress named Marla Sokoloff for like four years, she was on that show The Practice. She played the secretary. We did a movie together. A really bad movie called Whatever It Takes."
Sokoloff is now married to drummer Alec Puro and they have a daughter together.