Mercedes Ruehl was born on February 28, 1948, in Jackson Heights, Queens, New York City, to Mercedes J. Ruehl, a schoolteacher, and Vincent Ruehl, an FBI agent.

Her father was of German and Irish descent, while her mother was of Cuban and Irish descent. Growing up, the family moved frequently due to Vincent Ruehl's assignments with the FBI, and they lived in various states including Silver Spring, Maryland. Ruehl and her brother, Peter, were raised Catholic.

Mercedes Ruehl attended the College of New Rochelle and graduated in 1969 with a BA in English. She began her acting career in New York City, appearing in various off-off Broadway productions while working temping and waitressing jobs.

She established herself in regional theatre with the Denver Center Theatre Company. Her first starring role on Broadway came in 1984's "I'm Not Rappaport," and she won the 1984 Obie Award for her performance in "The Marriage of Bette and Boo".

Her career took off with her acclaimed performance in the play "Lost in Yonkers," for which she won the 1991 Tony Award for Best Actress (Play).

She also received a 1991 Academy Award for Best Supporting Actress for her role in the film "The Fisher King," where she played a strong-willed and pragmatic video store owner. Her other film credits include "Big" (1988), "Married to the Mob" (1988), "Last Action Hero" (1993), "Roseanna's Grave" (1997), "Gia" (1998), "The Minus Man" (1999), and "Hustlers" (2019).

Mercedes Ruehl has appeared in television shows such as "Law & Order" and "The Sopranos." She was married to abstract expressionist painter David Geiser from 1999 until his death in 2020, and they had one daughter. Her brother, Peter Ruehl, was a respected journalist and columnist who passed away in 2011.

Her accolades include an Academy Award, a Golden Globe Award, a Tony Award, a Drama Desk Award, two Obie Awards, and two Outer Critics Circle Awards.