Brooklyn's Stephen Dennis drew a foul with 5 seconds left to play and the game tied at 96-all, but he missed both free throws. Teletovic was there for the offensive rebound and was fouled by Rob Kurz. Teletovic made the first foul shot, then missed the second and Boston called a timeout with 3.6 seconds left.
Boston got two more shots off, but missed both.
Pierce and Garnett sat out the fourth quarter and the Brooklyn reserves made a run on Boston's, taking a 96-95 lead on Tornike Shengalia's three-point play with 41 seconds left.
The Celtics and Nets play a preseason rematch Thursday night in Brooklyn.
Detroit Pistons guard Darrun Hilliard will not participate in summer league because of a stress fracture of his lower back.
The Milwaukee Bucks have added a year to general manager John Hammond's contract, which keeps him in his role through 2017-18, according to multiple reports.
The NBA and the Charlotte Hornets expressed doubt Thursday that possible changes to House Bill 2, a law limiting protections for LGBT people, would go far enough.