James finished with 26 points, 13 assists and 11 rebounds in Game 5 of the title series Thursday night, leading the Miami Heat to a 121-106 victory over the Oklahoma City Thunder.
Miami won the second title in franchise history, and James won for the first time in three finals appearances.
James and the Cleveland Cavaliers were swept by the San Antonio Spurs in 2007, then he and the Heat fell in six games to the Dallas Mavericks last season.
Asked Thursday what the title meant, James said, "It means everything."
On Friday, James tweeted: "OM*G I think it just hit me, I'm a CHAMPION!! I AM a CHAMPION!!"
Information from The Associated Press was used in this report.