The Heat won despite playing without stars LeBron James, Dwyane Wade and Ray Allen, who were held out while recovering from injuries.
The 33-year-old Miller was 7 of 11 from beyond the 3-point arc.
Chris Bosh chipped in with 18 points and eight rebounds, and Rashard Lewis added 14 points for Miami, which improved to 3-2 since Chicago snapped its 27-game winning streak.
Miami (59-16) is within three victories of setting a new franchise record for wins in a regular season.
Rookie Michael Kidd-Gilchrist had 18 points and 14 rebounds for the Bobcats, who lost for only the second time in their last seven home games.
The Heat held Gerald Henderson and Kemba Walker to a combined 5 of 31 shooting from the floor.
Miami owns the best record in the NBA and the Bobcats have the worst. But the playing field was leveled to some degree with James, Wade and Allen
-- who average a combined 59 points -- sitting out with Miami already having clinched the No. 1 seed in the Eastern Conference playoffs.
It didn't seem to bother the Heat, who relied heavily on the 3-pointer while staking to a 48-45 halftime lead. Led by Miller's sharpshooting, Miami was 10 of 22 from 3-point range before the break.
Meanwhile, the Bobcats shot just 36 percent in the first half and were 1 of 7 from behind the 3-point arc.
Charlotte shot 32 percent for the game.
The Heat opened a 13-point lead in the third quarter behind some stifling defense and weren't seriously challenged again.
Charlotte managed just 10 points in the third period on 3-of-18 shooting and turned the ball over five times. Most of Charlotte's shot attempts were heavily contested and the Bobcats appeared completely out of sync at times.
Henderson has been a catalyst for the Bobcats in recent weeks, averaging 22.9 points on 51 percent shooting over the past 14 games. He started out strong with eight points in the first quarter but quickly went cold and failed to score in the second and third quarters.
He got frustrated with the officiating, even drawing a technical foul in the second half. Henderson finished with 11 points on 2-of-16 shooting.
Walker had 12 points and shot 3 of 15.
Mario Chalmers returned for the Heat after missing the last three games with a sprained ankle and finished with four points and seven assists.
NOTES: This is the first time James has missed three consecutive games since signing with the Heat. ... The arena erupted with cheers when James and Wade entered the court in street clothes with 5:47 left in the first quarter. ... Mike Hatchett Jr., a Bobcats fan from Columbia, S.C., won $7,777 when he swished a shot from halfcourt during a casino-sponsored promotion in the fourth quarter.
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