The center had been a free agent after being waived by the Chicago Bulls, who had traded for him from the Cleveland Cavaliers at the start of the year.
General manager Kevin Pritchard told the Indianapolis Star: "He made it perfectly clear. He was like, 'Look, I want to win a championship, I think I can really help you, and I want to fit in. I'm not coming here to let everybody fit in with me. I got to fit in with everybody else. When he said that I think the thing changed."
Bynum has averaged 8.4 points per game this season.