With a little more than eight minutes remaining in the fourth quarter and the Heat leading 83-79, the fan entered the court during a Cavaliers possession from the baseline near Miami's bench. He appeared to touch James before he headed out near the three-point line, where he displayed a shirt that read "We Miss You" on the front and "2014 Come Back" on the back.
The fan was eventually bearhugged by a security officer and escorted off the court without further incident.
The Palm Beach Post reported James' version of the unusual encounter.
“Well, he said he missed me,” James said. “And come back please. And I didn’t have much time to say much to him, because security got to him.”
"This was one of most bizarre, unique days of my life with everything that happened. It also was one of the best comebacks I've been part of.”
James, who left Cleveland for Miami in 2010, has an early-termination option in his contract that would allow him to become a free agent in 2014.
Rumors have trickled out in recent months that James might look to make a homecoming of sorts after achieving his goal of winning a title in Miami. ESPN.com reported this week that James, a native of Akron, Ohio, remains noncommittal about his future.
"My only focus now is to win another championship, I can't worry about speculation or rumors," James said recently when the subject was raised. "What we're doing on the floor right now is what it's all about. We're playing good ball right now. We're trying to win a championship."
Cavaliers owner Dan Gilbert, who famously ravaged James for leaving Cleveland, tried to dispel the rumors on Twitter.
"Cleveland Cavaliers young talent makes our future very bright," Gilbert wrote on Wednesday. "Clearly, LeBron's is as well. Time for everyone to focus on the road ahead."
The Heat rallied from a 27-point deficit to extend their winning streak to 24 games. James finished with a triple-double of 25 points, 12 rebounds and 10 assists (all game highs) in 42 minutes.
Miami improved its league-best record to 53-14. Cleveland, playing without the injured Kyrie Irving, Anderson Varejao and Dion Waiters, dropped to 22-46. Wayne Ellington finished with 20 points, seven rebounds and four assists for Cleveland.