The Rockets hadn't lost since Jan. 27 and put together the NBA's second-longest winning streak. It ended 11 victories shy of the 1971-72 Lakers, who won 33 in a row.
"I'm too close to the situation right now to really appreciate," the Rockets' Shane Battier said. "When I'm old and gray and can't dribble this basketball anymore, I think I'll appreciate it. Right now, we're still in a playoff run and have got some dogs barking at our heels."
The Rockets also lost for the first time in 11 games since Yao Ming suffered a season-ending foot injury on Feb. 26.
Luis Scola scored 15 for Houston, which also had a 15-game home streak ended. Only the 1985-86 Rockets, who won 20 straight, had a longer home-court streak in franchise history. Tracy McGrady had only eight points on four-for-11 shooting.
Leon Powe scored 21 points to help Boston win for the 13th time in its last 14 games.
The Rockets, who also fell back into a first-place tie with the Lakers atop the Western Conference, scored a season-low 34 points in the second half on 11-for-33 shooting.
The Rockets still have one streak to protect -- they'll go for their 13th straight road win in New Orleans tonight.
Meanwhile, Garnett responded after the game to Minnesota Timberwolves owner Glen Taylor's belief that Garnett "tanked it" by sitting out the final five games of last season for what was described then as a leg injury.
"Glen Taylor was good to me while I was a Timberwolf. I'm a Boston Celtic now. I'm not going to be going back and forth and saying tasteless things," Garnett said.