James, 34, is a 15-time All-Star, four-time NBA MVP and a three-time NBA champion, who just finished his 16th season in the league. He also has an annual basketball salary of more than $35 million, not including his many lucrative endorsements and ventures in Hollywood.
Forbes estimates James' net worth at $450 million, while his career earnings have passed the $1 billion mark.
Buffett -- who is worth more than $80 billion -- wrote about the Los Angeles Lakers star in an article for TIME's 100 most influential people of 2019.
He said he first met James more than 10 years ago while he was filming a skit for his company, Berkshire Hathaway. James impressed Buffett with his leadership skills, sharp mind and ability to stay grounded.
"Early heroes will mold a person's future," Buffett wrote. "LeBron has justified the adulation of millions and millions of young people, thanks to his ability to live up to enormous expectations on the basketball court, his business successes in Hollywood and media, and his new I Promise School for disadvantaged kids in his hometown of Akron, Ohio."
"That adulation will make a positive difference in their lives. And you know what else is exciting? As great as he has been so far -- on and off the court -- you're just seeing the start of LeBron."
James is signed with the Lakers through 2021, with a $41 million player option in the final year of his contract.