Bennett was bisexual. He had numerous affairs with both men and women. In his younger days, Bennett had a relationship with Larry Fuller, a dancer, choreographer and director. He had a long professional and personal relationship with the virtuoso dancer Donna McKechnie, who danced his work in both "Promises, Promises" and "Company" and won the 1976 Tony Award for Best Actress in a Musical in the role he had created for her in "A Chorus Line". They married on December 4, 1976, but after only a few months they separated and eventually divorced in 1979.