James, who left Cleveland in July as a free agent and signed with Miami, posted to his Twitter account after his team's 112-57 victory over the Cavaliers in Miami, the South Florida Sun-Sentinel reported Wednesday.
The tweet read: "Crazy. Karma is a b****. Gets you every time. It's not good to wish bad on anybody. God sees everything!"
James said before the game the "villain" persona he recently adopted was a "joking thing" inspired by the jeer-filled reception Miami has been getting from fans at away games.
"It's not like I really feel like a villain. It's just when I go into an opposing building, it's nothing but venom thrown at us, so you know you embrace that," James said.
Cavaliers owner Dan Gilbert made a reference to karma in a statement released after James announced his decision in July.
"This heartless and callous action can only serve as the antidote to the so-called 'curse' on Cleveland, Ohio. The self-declared former 'King' will be taking the 'curse' with him down south. And until he does 'right' by Cleveland and Ohio, James (and the town where he plays) will unfortunately own this dreaded spell and bad karma. Just watch," Gilbert wrote on the team's Web site.