Pierce shot 10 of 20 from the field, made 15 of 18 free throws and added 10 rebounds and four assists.
Pierce has scored 20 or more points in five of the past six games and is averaging 22.3 points per game during March.
Kevin Garnett had 24 points for the Celtics.
Gerald Henderson had 21 points for the Bobcats (7-40), who have lost six of their past seven and remain the only team in the NBA with fewer than 10 wins. Charlotte got 59 points from its bench, including 18 from Byron Mullens and 16 from Derrick Brown.
The Celtics have the same record (27-22) as the 76ers with 17 games remaining in the regular season.
Boston seemed poised to put this game away early.
With the game tied at 13, the Celtics went on a 14-0 run with Pierce, Garnett and Rajon Rondo combining for 12 points — most of those coming inside the paint.
They stretched the lead to 33-15 by the end of the first quarter, taking advantage of the Bobcats inability to score. Charlotte shot 29 percent from the field and didn’t hit a field goal in the final 6:47 of the first quarter.
But Charlotte showed some fight, pulling to within 52-50 at halftime as Mullens and Reggie Williams began to heat up from the outside. The Bobcats improved in the second quarter, shooting 65 percent to get back in the game.
Boston led by as many as 12 in the second half but the Bobcats stayed close, closing the gap to four late.
However, Pierce scored on a pretty crosscourt feed from Rondo and Garnett knocked down a jumper from the top of the key to seal the victory.
Rondo finished with 13 assists, seven points and six rebounds.
NOTES: Bobcats coach Paul Silas picked up his seventh technical foul of the season during the first quarter, giving him seven for the season — one behind league leader Celtics coach Doc Rivers.