BOSTON — The Boston Celtics can wrap it up on the road, where they haven’t won yet. Or they can finish Cleveland off at home, where they haven’t lost.

Two chances for the one win they need to reach the Eastern Conference finals.

“This momentum, and what we did here tonight,” Kevin Garnett said, “we’ve got to figure a way to carry this on the road.”

Garnett scored 26 points with 16 rebounds on Wednesday night as the Celtics beat Cleveland 96-89 to take a 3-2 lead in the best-of-seven conference semifinals.

Game 6 is Friday night in Cleveland.

“We know it’s a win-or-go-home situation. We’ve got to approach it that way,” said LeBron James, who scored 23 of his 35 points in the first 20 minutes and then went cold again. “We’re a very good team at home. But a LeBron James team is never desperate.”

Paul Pierce scored 29 points and helped shut James down for much of the second half. The Cavaliers forward had 23 points with 3:50 left in the first half but made just one basket in the next 20 minutes as Boston erased a 14-point deficit and took the lead for good.

James, who shot under 26 percent in the first four games, was 12-of-25 from the field but made just four of his last 14 shots and missed all five of his 3-pointers.

“Whether we get 35 or 20 (from James), it doesn’t matter at this point,” Cavaliers coach Mike Brown said. “To lose the game ... that’s what’s more disappointing than anything else. Whether he gets this or that, I’m not really concerned, because he’s going to contribute in other ways.”

Cleveland cut an 88-77 lead to 91-87 on two free throws by Delonte West with 46 seconds to play. But, after running down the shot clock, Garnett got the rebound of his own miss and Pierce hit five free throws in the last 16 seconds to ice it.

The Celtics are undefeated at home but they have yet to win on the road, a streak that allowed the eighth-seeded Atlanta Hawks to go the distance in the first round and let Cleveland back in this series after Boston won the first two games.

“We’re going to get one. I don’t know when,” coach Doc Rivers said. “It would be great if it’s Game 6.”

Boston, which had an NBA-best 66-16 record in the regular season, has the home-court advantage throughout the playoffs. But no team has ever won a title without winning an away game.

In fact, Boston could be the first team to advance through the second round without a road win.

“They have a good cushion, being the best team in the NBA,” Cavaliers center Zydrunas Ilgauskas said. “They really don’t have to win on the road. Hopefully, we can take care of our business at home and come back here and have another shot.”

Cleveland took a 43-29 lead in the second quarter thanks to eight straight points from James. But Rajon Rondo hit back-to-back 3-pointers as the Celtics scored 14 of the last 17 points in the first half, then took the lead with the first four points of the third quarter.

James made eight of his first 11 shots and seemed to snap out of his series-long shooting slump. But he made just one basket in the third, a baby hook with 45 seconds left in the quarter, and he scored eight in the last five minutes after Boston already led by 12.

West had 21 points for Cleveland, which missed 10 free throws in the second half. Ilgauskas was held to playoff-low six points.

Notes: West (eyes) and Ben Wallace (dizziness) left the court for the Celtics’ introductions to avoid the smoke that accompanies the pregame fireworks. West said he went to an eye specialist after Thursday’s shootaround. “It’s hard to play this game with one eye unless you’re a pirate,” he said. ... The Celtics scored 12 points in the fourth quarter of Game 4 and 22 in the first 16 minutes of Game 5, giving them 34 points in a 28-minute span. ... Daniel Gibson went to the locker room in the fourth quarter with a bruised left shoulder. He is scheduled for an MRI in Cleveland on Thursday. ... Celebrities in the crowd: Rob Lowe, Jay-Z, Beyonce, Louis C.K., Jonah Hill (Superbad), Donnie Wahlberg, JoJo Levesque and various New England Patriots.