Lebron James and teammates set to work defending their title with a 120-107 win over their rivals, but the LA Lakers crashed to an opening day defeat against Dallas.
NBA: Miami Heat begin title defence with victory over Celtics
Miami were presented with championship rings before the game to mark their second NBA title and the first since the creation of the 'Big Three' with the arrival of Lebron James and Chris Bosh to team up with Dwyane Wade.
Ray Allen made his Miami debut against his old team and put aside any concerns about his fitness with 19 points as the home crowd taunted the Celtics with chants of "We got Ray!".
Last season's Most Valuable Player James marked his first ring ceremony with 26 points but had to sit out most of the fourth quarter with leg cramps.
Wade top scored with 29 points, while Bosh delivered down the stretch and finished with 19 points.
Miami were 19 points up early in the fourth but, in the absence of James, Boston launched a comeback and reduced the deficit to four with just over two minutes remaining on the clock.
The Heat rallied, however, to gain a win against the team they defeated in last year's Eastern Conference championship game.
Paul Pierce had 23 points and Rajon Rondo 20 for the Celtics.
The heavily anticipated new era of Los Angeles Lakers basketball began with a whimper on Tuesday as their much vaunted team bristling with All-Stars were beaten 99-91 by an under-strength Dallas Mavericks.
Five-time NBA champion Kobe Bryant had given the Lakers a late boost when he pronounced himself fit enough to play in the regular season opener shortly before the game, having struggled with a foot injury for more than a week.
Though Bryant scored 22 points on 11-of-14 shooting and Spanish forward Pau Gasol weighed in with a game-high 23, the Lakers paid the penalty for a dismal free-throw display, making only 12-of-31.
The Mavericks were without 11-time All-Star Dirk Nowitzki, who is recovering from knee surgery, and injured center Chris Kaman but in their absence, six Dallas players scored at least 10 points with guard Darren Collison leading the way with 17.
Brandan Wright contributed 14 and fellow forward Shawn Marion 11 as the Mavericks stunned the 16-time NBA champion Lakers despite being out-shot from the field by 49.4 percent to 47.1.
Huge cheers erupted when former Orlando Magic center Dwight Howard led the Lakers out onto the court for their warm-up, and even louder roars for Bryant, the last player out.
Shortly before tip-off, Bryant walked to the middle of the court with microphone in hand and said: "There's a lot of expectations this season so we will to try and bring another championship back home to Los Angeles. Let's get this party started! Enjoy the show."
With Bryant, Howard and Gasol all getting into the paint early on, the Lakers made an encouraging start and led by eight points after an Antawn Jamison layup less than a minute into the second period.
However, a rash of missed free throws and turnovers cost the Lakers dearly. They trailed 48-46 at halftime and were never able to close the gap after that as the faster Mavericks steadily increased their lead.
Two O.J. Mayo free throws late in the fourth quarter gave Dallas a 16-point advantage, the biggest of the night, and though the Lakers scored nine of the last 10 points, it was a case of too little too late.
Six-time All-Star Howard, still easing his way into form after having back surgery in April, produced 19 points while twice former Most Valuable Player Steve Nash contributed just seven, plus four assists, on their Lakers debuts.
At Cleveland, Kyrie Irving scored 29 points and Anderson Varejao had a career-high 23 rebounds as the Cavaliers opened the season with a 94-84 victory over the short-handed Washington Wizards in the first game on the NBA schedule.
Rookie Dion Waiters added 17 points for the Cavs, who led by 16 in the third quarter but needed big plays from Irving and Varejao in the final minutes to hold off the Wizards. Varejao had a career-high nine assists, two setting up dunks by Tristan Thompson in the last two minutes.
Jordan Crawford scored 11 points to lead the Wizards, who were without star point guard John Wall, power forward Nene and forward Kevin Seraphin. Wall is expected to be out until late November with a knee injury.