Larry Hughes added 17 points, six helpers and four steals for the Cavaliers, who were coming off a sweep of Washington in the first round.
Sasha Pavlovic chipped in with 15 points while Drew Gooden had 14 points and 14 rebounds for Cleveland, which dominated the backboards with a 51-37 overall edge and a 20-9 advantage on the offensive glass.
"A couple of days ago, I started not felling too well," said James. "But, it’s the playoffs and you have to battle through it. No matter what it took, I was going to be out on the court helping my teammates get a win. I hope I can just continue to get well and continue to get my strength back."
Vince Carter tallied 21 points, 13 rebounds and six assists but shot just 7- of-23 from the floor for the Nets, who knocked out the Toronto Raptors in six games during the first round. Richard Jefferson finished with 16 points while Bostjan Nachbar had 12 points off the bench.
Jason Kidd flirted with a triple-double, scoring seven points, grabbing 10 rebounds and dishing out nine assists but shot a miserable 2-of-11 from the field.
"We knew (offensive rebounding) was something that we had to focus on and they had 20 of them," Kidd said. "We have to address that tomorrow and look at the film. They had quite a few possessions where they had multiple shots."
Game 2 of the series is scheduled for Tuesday in Cleveland.
The game was even heading into the final frame and Kidd quickly tried to set the tone by draining a three from the left wing to make it a 62-59 game.
But, Cleveland didn’t waver. A Zydrunas Ilgauskus lay-in deadlocked things again at 67 with 8:36 left. Nearly four minutes later, a Hughes triple put the Cavs in front, 74-69.
The Nets looked like they would get right back into it with under two minutes left. Kidd made steal and looked like he was headed for an uncontested layup but Pavlovic swooped in from behind to swat the ball away.
"I lost the ball on that pass and I just didn’t give up on the play," Pavlovic said. "It was very important. I knew Jason probably was not going to dunk so I just followed him and tried to get the ball."
New Jersey kept battling back, however, and Carter drained a pair from the line to draw the Nets within a bucket with just 32 ticks left.
James had the answer, however. The superstar took Kidd on the blocks for a running jumper with 19.5 seconds left. Then, he tortured Jefferson at the other end, blocking a shot and eating up precious seconds. The Nets finally got the ball back but Jefferson rimmed a three as time expired.
"It was a hard fought game," said Cavs coach Mike Brown. "Our guys did a terrific job fighting and getting stops down the stretch."
The Cavs spread the ball around nicely in the first quarter and led 23-20 after the opening 12 minutes.
New Jersey rebounded with the first significant run of the game to open the second quarter. The Nets ran off a 13-2 spurt, capped by a Josh Boone lay-in, to see-saw on top, 33-25, with just under eight minutes until intermission.
Cleveland finished strongly, however. The Cavs outscored New Jersey 18-8 the rest of the way. Hughes’ jumper finished the scoring in the frame with Cleveland holding a precarious two-point edge, 43-41.
Things remained tight throughout the third quarter. Mikki Moore got loose on the baseline for a driving dunk that put the Nets on top, 57-54, with 3:55 left in the stanza.
The Cavs came right back again and deadlocked things at 59 heading to the final frame.
Game Notes
The Nets shot just 37 percent in the game...This is the third time the Cavaliers and New Jersey are meeting in the postseason. Cleveland defeated the Nets twice in the first round. The Cavs knocked out the Nets in four, 3-1, in 1992 and in five, 3-2, in 1993...Cleveland is 2-2 all- time in the Eastern Conference semifinals. The Cavaliers defeated Washington in seven games in 1976 and beat the Celtics in seven in 1992. They were swept by the Bulls in 1993 and lost in seven to Detroit last year...The Nets have lost their last two trips to the Eastern Conference semifinals. They were ousted in seven by Detroit in 2004 and in five by Miami last season. New Jersey is 2-3 all-time in the East semis.