Beal was the star of the show at the Quicken Loans Arena as he scored 25 points, with rookie Kelly Olynyk also grabbing 25 and notching a season-best 12 rebounds.
"Wins like this mean a lot because it shows that we're going to continue to go out and play hard," Bradley told reporters after the game.
"We feel like we still have something to play for. We might have had some defensive breakdowns, but we played hard the whole time."
The victory sees the Celtics sitting in fourth position in the Atlantic Division with a record of 25-55 for the season.