Carroll was born Patricia Ann Carroll in Shreveport, Louisiana, on May 5, 1927, to Maurice Clifton Carroll and Kathryn Angela (née Meagher) Her family moved to Los Angeles when Pat was five years old and she soon began acting in local productions. She graduated from Immaculate Heart High School and attended Catholic University of America after enlisting in the United States Army as a civilian actress technician.
In 1956, Carroll won an Emmy Award for her work on Caesar's Hour and was a regular on the sitcom Make Room for Daddy from 1961 to 1964. She guest starred in the drama anthology series, The DuPont Show with June Allyson. Carroll also appeared on many variety shows of the 1950s, 1960s and 1970s, such as The Red Buttons Show, The Danny Kaye Show, The Red Skelton Show, and The Carol Burnett Show. In 1965, she co-starred as "Prunella", one of the wicked stepsisters in the 1965 production of Rodgers and Hammerstein's musical version of Cinderella.
In the late 1970s Carroll's successful one woman show on Gertrude Stein, Gertrude Stein, Gertrude Stein, Gertrude Stein (by playwright Marty Martin), won several major theater awards, her recorded version won a 1980 Grammy Award for Best Spoken Word, Documentary or Drama.
In early 1976, Carroll was cast as Lily, the mother of Shirley Feeney (played by Cindy Williams) in the episode, "Mother Knows Worst" on the hit ABC situation comedy, Laverne & Shirley. She portrayed Pearl Markowitz, the mother of Adam Arkin's character Lenny Markowitz, in the 1977 CBS situation comedy Busting Loose. Her frequent television roles in the 1980s included newspaper owner Hope Stinson on the syndicated The Ted Knight Show (the former Too Close for Comfort) during its final season in 1986; and that of Gussie Holt, the mother of Suzanne Somers' lead character in the syndicated sitcom She's the Sheriff (1987–1989).
Since the late 1980s, Carroll has had a great deal of voice-over work on animated programs such as A Pup Named Scooby-Doo, Galaxy High, Foofur and A Goofy Movie. On TV's Pound Puppies, she voiced Katrina Stoneheart. On two Garfield television specials (A Garfield Christmas and Garfield's Thanksgiving), she voiced Jon's feisty Grandma. She also voiced the character of Granny in the 2005 re-release of Hayao Miyazaki's My Neighbor Totoro.
In 1989, Carroll portrayed the sea witch Ursula in Disney's The Little Mermaid and sang the song "Poor Unfortunate Souls". In interviews, Carroll has referred to the role as one of the favorites of her career. She has since reprised the role in other forms of media, including the Kingdom Hearts series of video games, the spinoff television series, and in various Disney theme parks attractions and shows. She also voiced Ursula's sister Morgana in The Little Mermaid II: Return to the Sea, the direct-to-video sequel released in 2000.
Carroll also appeared on a variety of game shows including Celebrity Sweepstakes, You Don't Say, To Tell the Truth, Password and I've Got a Secret.
A member of the Actors Studio, she has also had a successful career in the theater, appearing in numerous plays including productions of Our Town and Sophocles' Electra. In 1990, she starred in The Merry Wives of Windsor at the Shakespeare Theatre at the Folger in the role of Sir John Falstaff, a balding knight with whiskers.
When Drama critic Frank Rich of The New York Times reviewed her performance he wrote: "Her performance is a triumph from start to finish, and, I think, a particularly brave and moving one, with implications that go beyond this one production. Ms. Carroll and Mr. Kahn help revivify the argument that the right actresses can perform some of the great classic roles traditionally denied to women and make them their own. It's not a new argument, to be sure; female Hamlets stretch back into history. But what separates Ms. Carroll's Falstaff from some other similar casting experiments of late is that her performance exists to investigate a character rather than merely as ideological window dressing for a gimmicky production."
Patricia Ann Carroll participated in the U.S. Army as a nurse after the Vietnam War. She was sent across the world to Vietnam as a medical personnel. She graduated from The Catholic University of America in 1950. However, her stage debut was in 1947.
Carroll married Lee Karsian in 1955 and they had three children - two daughters, Kerry and Tara Karsian and a son, Sean. In 1991 Carroll received an honorary doctorate from Siena College in Albany, New York.