McNair died Sunday after a battle with throat cancer in Los Angeles, sister Jacqueline Gaither said.
"She was very family oriented," Gaither said. "She was more than just a star or a famous personality. She was a person of her own."
Gaining fame in the 1960s as a nightclub singer, McNair graduated to film and television as opportunities were opening up for black women late in the decade. She made her Hollywood acting debut in 1968 in the film, "If He Hollers, Let Him Go."
She later starred with Elvis Presley in his 1969 film "Change of Habit" and as Poitier's wife in the 1970 film "They Call Me MISTER Tibbs!"
She found movie acting "a more rewarding kind of work than singing," she told The Washington Post in 1969. "When I'm working in a club, I must go from one song to another rapidly and I don't have much time to express myself emotionally. In a movie, you can concentrate on one scene at a time."
She hosted television's "The Barbara McNair Show," a syndicated musical and comedy program, from 1969 to 1972.
As a singer, one of her biggest hits was "You Could Never Love Him." She started out as a jazz singer but later branched out, adding show tunes and the Beatles' "Yesterday" to her repertoire.
Gaither said her sister seemed headed for a career in show business from the time she was a girl in Racine, Wis.
"She sang from the time she was 5 years old in churches and then at school," Gaither told the Racine Journal Times. "We always encouraged her."
McNair went to the University of California, Los Angeles, before moving to New York City to pursue her dream of becoming an entertainer.
An engagement in 1957 at the Village Vanguard earning her the notice that would lead to her first Broadway performance in the play "The Body Beautiful" a year later. She went on to star on Broadway in the musical "No Strings" in 1963.
Reviewing a nightclub appearance in late 1965, a New York Times writer commented that the "strikingly beautiful" McNair "does not have to depend on looks alone. She is a highly knowledgeable performer who projects an aura of beauty, a warm personality and an appealing sense of fun."
As she gained notice in Hollywood in the late 1960s, she told the Post that a steamy 1968 photo spread she did for Playboy "helped my career immensely."
Also around that time, she joined a Bob Hope tour to entertain servicemen in Vietnam, saying she was thrilled to later meet men who had seen her there. "I don't believe in war for any reason," she told the Post. "I went over there to see what war was like and to comfort the men and I was appalled."
Her career was hampered in 1972, when she was accused of drug possession along with her husband after she signed for a package delivered to her dressing room. She was later cleared.
"You can spend all this time building something and it can be destroyed in a minute," she told the Post in 1979.
McNair sang professionally as long as she could, Gaither said, but the cancer that started in her throat and then spread eventually hurt her ability to perform.
"She sang until the middle of last year," Gaither told the Journal Times. "At that time she thought that would be her last. The audience enjoyed her, but she did not think she was really doing well at that time. She said that if she couldn't sing any better than that, that would be the last one."