Allen's 3-pointer with 4:42 left in the third quarter Sunday night allowed him to break the mark he shared with Scottie Pippen and Kenny Smith.
"I didn't think it was easy, getting the 3's up in the air," Allen said. "You look up and everybody is probably thinking, 'How did this guy get open?' But there's so much going on there -- big screens, misdirection plays. I thought they did everything they could to keep me from shooting 3's, [but we] worked tirelessly."
Allen connected on the first seven 3-pointers he attempted in Sunday's game before one rimmed out late in the first half. Allen finished 9-of-14 shooting for 27 points in the first half. Of Allen's nine makes, six were assisted by Rajon Rondo.
He finished the night with 32 points as the Celtics beat the Lakers 103-94 to even the best-of-seven series at 1-1.
Allen also had made seven 3-pointers in a game against the Lakers two years ago.
Limited to 27 minutes due to early foul trouble in Game 1, Allen never got in a rhythm, connecting on 3-of-8 shots, but no 3-pointers, while finishing with 12 points.
Chris Forsberg covers the Celtics for ESPNBoston.com. Information from The Associated Press contributed to this report.