Randall was born Leonard Rosenberg in Tulsa, Oklahoma on February 26, 1920 and graduated from Tulsa Central High School before studying at Northwestern University, Columbia University, and with Sanford Meisner at the Neighborhood Playhouse. He made his Broadway debut in A Circle of Chalk in 1941; his later Broadway credits included Inherit the Wind, Oh Captain!, UTBU, and M. Butterfly.
He made a splash in Hollywood with his performance in the film version of Will Success Spoil Rock Hunter? and appeared in such later movies as No Down Payment (opposite Joanne Woodward) and Let's Make Love (opposite Marilyn Monroe). In Pillow Talk, Send Me No Flowers, and Lover Come Back, Randall romped with Doris Day and Rock Hudson. His most recent film role was in the 2003 release Down With Love.
Randall is almost certainly best known and most beloved for his Emmy-winning portrayal of Felix Unger in the television series based on Neil Simon's Broadway comedy The Odd Couple. That show ran from 1970-1975; his other TV credits include One Man's Family, Mr. Peepers, and The Tony Randall Show, which ran from 1976-1978. He also portrayed the openly gay character in the television movie Sidney Shorr and in Love, Sidney, the TV series based on it.
In 1991, Randall launched the National Actors Theatre, a not-for-profit, subscription based company. Its most recent effort was a 2003 production of Pirandello's Right You Are -- one of the many NAT shows in which Randall co-starred -- at the Michael Schimmel Center for the Arts at Pace University.
Randall is survived by his wife, actress Heather Harlan, whom he met while she was interning at the National Actors Theatre, and their two children. His previous wife, Florence Gibbs, died in 1992; the couple had been married for 54 years.