But rookie Norris Cole scored 14 of his 20 points in the fourth quarter, including eight of Miami's final nine points to help seal the 115-107 Heat win.
The Heat have won two straight regular-season meetings with the Celtics after losing the previous eight meetings.
The "Big Three" of Dwyane Wade, LeBron James and Chris Bosh combined for 68 points on 62.5 percent shooting Tuesday. Nearly 48 percent of their shots came inside five feet, where they made 16 of 19 field goals. Last season, the trio attempted 36 percent of their field goals inside five feet.
The Celtics were able to close the gap in part because the Heat stopped attacking the basket in the fourth quarter, settling for jumpers from 20 feet and beyond on 10 of their 21 attempts.
Pct of FGA By Distance
Tuesday vs Celtics
With less than three minutes remaining in the third quarter, Doc Rivers switched to a zone defense, and the Heat struggled to adapt.
Boston played zone on just two percent of all plays last season, but had success with it Tuesday. Miami's half-court offense was effective against man-to-man, shooting better than 60 percent in the half court, but the Heat were held under 30 percent against the zone.
Miami Heat Half-Court Offense
Tuesday vs Celtics
While their offense stalled in the half court against the zone, Miami’s not having trouble playing its desired style so far this season.
The Heat are averaging 102.5 possessions per game, well above their 2010-11 season average of 93.2 (21st in NBA).
Miami had 104 possessions against the Celtics Tuesday night, making it the Heat's fastest regulation game in the last two years.
James finished with 26 points, six rebounds and five assists. James has 63 points in his first two games, a Heat record for most points in the first two games of the season.
But James scored two points in the fourth quarter, attempting just two shots. Dating back to the NBA Finals, James has failed to score more than five points in the fourth quarter in eight straight games.