Born on March 30, 1922 in Westfield, Massachusetts, Pitoniak graduated from what is now the University of North Carolina at Greensboro. She spent two years as a civilian actress immediately after World War II, touring Japan, the Philippines and Korea for the Army's Special Services division. She met her future husband, Jerome Milord, then a soldier, when they were both in a U.S.O. show in Japan.
In 'night, Mother, which opened in 1983, she played a woman who desperately tries to keep her daughter from killing herself. The play had its premiere at the American Repertory Theatre in Cambridge, Massachusetts, then moved to Broadway. Both Pitoniak and co-star Kathy Bates received Best Actress Tony Award nominations for their work.
In 1994, Pitoniak received a second Tony nomination for her performance as Helen Potts in the Roundabout Theatre Company's revival of Picnic. She also appeared on Broadway in Agnes of God, The Octette Bridge Club, Amy's View, Uncle Vanya, Dance of Death, and Imaginary Friends.
She performed frequently at the Actors Theatre of Louisville, in such plays as Norman's Getting Out, D.L. Coburn's The Gin Game, and Jane Martin's Middle Aged White Guys. She also worked steadily in film and television. (In the 1985 film version of Agnes of God, she appeared as the mother of Jane Fonda's character.)
In 2000, Pitoniak told TheaterMania: "I have never put 'actress' on any form of identification. I'm not trying to be coy, but I always felt that it would have been stretching things a bit to identify myself that way. But after Amy's View, for the first time, I felt that if I had to get a passport today, I'd put it down. I'd say that I am an actress."
She is survived by a son, Christian, and a daughter, Susan, as well as a grandson, two sisters, and a brother.