After graduating from high school in 1980, Gershon moved to Boston to attend Emerson College.
She transferred to New York University, and graduated with a BFA in drama and psychology/philosophy in 1983.
Gershon attended the Circle in the Square Professional Theater School in New York, working first with David Mamet and later with Harold Guskin and Sandra Seacat, whom she has described in interviews as "a huge influence." She has appeared on Broadway three times, as Sally Bowles in the revival of Cabaret, in the revival of the sex farce Boeing-Boeing, and played Rosie Alvarez in the 2010 Broadway revival of Bye Bye Birdie at the Roundabout Theatre Company.
She is known for her roles in the films Cocktail (1988), Showgirls (1995), Bound (1996), Face/Off (1997), The Insider (1999), Demonlover (2002), P. I Love You (2007), Five Minarets in New York (2010), Killer Joe (2011) and House of Versace (2013).She completed her high school from Beverly Hills High School. She later moved to Boston and started studying at Emerson College. From there she earned Bachelor of Fine Arts in drama and psychology in 1983.She has been active in the field of acting since 1981.Her break came with a bit part in Pretty in Pink (1986), which led to more substantial roles in Sweet Revenge with Nancy Allen and Cocktail with Tom Cruise and Elisabeth Shue and in John Sayles' urban drama City of Hope (1991).Gershon also worked in television, with a recurring role on Melrose Place playing a prostitute working for a Heidi Fleiss-esque Hollywood madam.