"It means a lot," James, aged 28 years and 17 days, told reporters. "I've been blessed to be able to stay healthy and play a lot of games. I'm grateful to have team mates to help me accomplish the feat."
James took the record from the LA Lakers' Kobe Bryant, who was 29 years and 122 days when he reached 20,000 points.
James also pitched in with 10 assists and seven rebounds against the Warriors, surpassing the 5,000 career assist mark during the first quarter.