They did not. It was actually three men depending on how one parses “first”. From NBA.com
“Not that long ago, it was a time when African-Americans could not take simple privileges — like staying at certain hotels or eating in certain restaurants — for granted. For Earl Lloyd, Chuck Cooper, and Nat “Sweetwater” Clifton, it was a time to make history.
Lloyd, Cooper, and Clifton entered the National Basketball Association in 1950 and became pioneers for today’s African-American basketball players. Cooper was the first African-American to be drafted by an NBA team. Clifton was the first to sign an NBA contract. And on Oct. 31, 1950, Lloyd, a member of the Washington Capitols, became the first African-American to play in an NBA game when he entered a game against the Rochester Royals.”