The Nets, who entered the game 5-52 and 2-27 on the road, took a 29-27 lead on Keyon Dooling's jumper at the end of the first quarter and never trailed again.
"Any win for us is big. There's no question," Nets coach Kiki Vandeweghe said. "But to get a win on the road, and this is one of the toughest places to play in the NBA just shows that -- it should demonstrate to our guys that if they play with effort, they can compete against anybody."
Kevin Garnett had 26 points and Marquis Daniels had 16 for the Celtics, playing their third straight game without Paul Pierce. The Celtics hope to get Pierce back for Tuesday's game against Detroit.
The Nets began the day with a win percentage of .088. The Celtics mark was .643. That's a difference of .555. Over the last 15 seasons, this was the fifth time that a team beat an opponent that had a win percentage at least .550 better than its own at least 50 games into a season.
Win Pct. Diff.
New Jersey took 41 free throws to the Celtics' 11.
"It shows that we were aggressive," Lopez said. "A lot of the season we've been settling for jump shots at very inopportune times. Tonight we were very assertive in trying to get to the basket and get the best possible shot we could."
Celtics coach Doc Rivers blamed his team for the free throw disparity, saying "it was on us."
Rivers said one of the things he told his team yesterday, a day after a 108-88 loss against the Cleveland Cavaliers, was "It ain't the system. It's our heads. It's between our ears. And we've got to come out and play."
Garnett said he was "disgusted" at the loss and said it came down to defense. "In this league you have to get stops, it's that simple. A team gets into a rhythm, and it's hard to turn it off."
New Jersey's effort shouldn't have come as a surprise to the Celtics. On Feb. 5 in Boston, the Nets hung with the Celtics until the last couple of minutes in a 96-87 loss.
The Celtics cut an 18-point fourth-quarter deficit to six on Ray Allen's 3-pointer with 2:05 left, but Kris Humphries' layup and two foul shots by Lopez ended the rally.
The Celtics didn't hit a 3-pointer until Nate Robinson's shot late in the third quarter and finished 3 of 19 from behind the arc while the Nets hit six 3-pointers in 13 attempts.
The Nets scored 25 points off 18 Celtics turnovers. Boston shot 63 percent in the first quarter and had a 12-2 lead, but the Nets, led by Harris' 11 points, charged back to take a 29-27 lead at the end of the quarter.
Lopez continued to hurt the Celtics inside in the second quarter and the Boston bench struggled. Lopez's tip-in with four minutes left in the first half gave the Nets a 46-36 lead.
New Jersey led 74-64 after three quarters and then started to pull away in the fourth. Chris Douglas-Roberts' dunk upped the lead to 12 with 7:44 left and Dooling's 3-pointer gave Jersey an 18-point advantage with five minutes left.
The flu has been bothering the Celtics, but Rivers dismissed it as a reason for the loss. "No, no, no. Everybody's sick right now. We just didn't play very well." ... New Jersey must win at least four of its remaining 24 games to overtake the 1972-73 76ers' 9-73 record.