Pierce and Garnett, who were traded to the Nets before the season after long stints with the Celtics, each scored six points for their new squad in their first visit to Boston since the deal.
Pierce played 15 years for Boston and Garnett joined him for six. They each were instrumental in Celtics' 2008 NBA championship.
Garnett helped seal Brooklyn's 10th win in 11 games when he stole a Rajon Rondo pass with 20.9 seconds left and followed with an uncontested layup at the other end for an 82-77 lead.
Brandon Bass had 17 points for Boston, losers of five in six games.