Pierce had been excused from the team for personal reasons and did not play in Monday's game against Minnesota, instead returning to Boston after Sunday's loss to the Knicks in New York. On Tuesday at 8:21 p.m. ET, Pierce, wife Julie and the pair's two daughters welcomed the baby boy.
Pierce revealed the new addition as part of a postgame interview with Boston sports radio WEEI.
On the court, Pierce finished with 17 points, five assists and three rebounds against the Pistons. He struggled with his shot -- 5-of-14 overall, while missing five of the six 3-pointers he attempted -- but was a team-best plus-8 in plus/minus as the Celtics topped the Pistons 98-93 at TD Garden.
Pierce has been nursing a sore right ankle that likely would have kept him out of Monday's game in Minnesota anyway (Celtics coach Doc Rivers had said Sunday he planned to rest Pierce that day). Pierce suggested he might sit out practice Thursday in order to get some additional rest.