Miami, beaten on the boards by a total of 38 rebounds over the previous three games, this time enjoyed a 50-39 advantage. Udonis Haslem had 12 rebounds and Chris Bosh added nine.
"There were some better in-traffic battles, guys going up and trying to get it with two hands, guys getting up off the ground," coach Erik Spoelstra said. "That disposition to rebound was better. It's an effort thing."
The game matched the teams with the best and worst records in the Eastern Conference, and in the late going it looked like it. Miami scored the final 21 points and held Washington scoreless over the last 7:07.
"The defense came alive," LeBron James said. "We understand that if we want to win, ultimately we have to defend."
James scored 24 points, extending his streaks of scoring at least 20 to 32 consecutive games this season, and 53 in a row including last year's playoff run.
James launched into a long jump in dismay when his dunk was waved off because of a Wizards foul. He gave the Heat a scare when he tweaked his left ankle and limped away from a scrum after drawing a foul, but he stayed in the game.
And there was no slackening in his scoring pace. He shot 9 for 17 and had seven assists.
The Wizards (4-28), last in the NBA in points and shooting, clanked a succession of open shots and hit only 36 percent. They lost their fifth game in a row and fell to 0-13 on the road against Eastern Conference teams.
Miami improved to 16-3 at home and now embarks on a six-game trip.
"We're going to see where we're at," Bosh said. "Trips are always a test."
As the Heat center, Bosh became a focus of criticism for their poor work on the boards. In response, he said, he kept track of his rebound total during the game.
"I'm just counting them so everybody will get off my back," he said with a chuckle. "It's nine today. OK. Now I need to get nine the next game -- or maybe even 10.
"The only way we can do a better job is if each guy challenges himself a little more, and I challenged myself tonight."
Spoelstra said he noticed a difference in Bosh, who sparked a fast start by Miami.
"I just like to see him get off the floor," Spoelstra said. "He probably had more jumps in this game than he has had in a lot of them. He was active. It felt like he was a 7-foot player, which he is."
Bosh finished with 17 points and a season-high four blocks. Ray Allen scored 20 off the bench and helped Miami pull away in the fourth quarter.
The Heat made their first seven shots to go ahead 15-6. The Wizards made several runs but never managed to pull even.
"Every time we came back, we got lazy," center Kevin Seraphin said. "We have to learn that every time we come back, we have to keep going to get stops."
The Wizards cut the margin to 78-71 midway through the fourth quarter but didn't score again, missing their final eight shots.
Allen made two 3-pointers and a three-point play down the stretch for the Heat. He finished 8 for 12.
"When you're not scoring and they're running, we're not making them take the ball out of bounds," Wizards coach Randy Wittman said. "That makes a difference."
Jordan Crawford, who leads Washington in scoring this season, went 1 for 7 and was held to two points. Seraphin led the Wizards with 14 points off the bench.
The crowd included New York Yankees slugger Alex Rodriguez, seated in the front row at midcourt next to Heat owner Micky Arison. ... The Heat begin their trip Tuesday at Indiana, where they're 9-35. ... The Heat had their best start shooting since Dec. 27, 2009 against the Pacers, when they made their first eight shots. ... Even with the loss, the Wizards are 3-3 against Miami over the past two seasons. ... Billy the Marlin drew scattered boos when he made an appearance to help celebrate Heat mascot Burnie's birthday. Fans are unhappy about the team's recent payroll purge.