"Tell LeBron to worry about Miami. It has nothing to do with Celtic business," Garnett said in response to James, who previously expressed thoughts that KG and Nets small forward Paul Pierce should apologize for criticizing Heat sharpshooter Ray Allen for leaving the Boston Celtics before they departed for Brooklyn.
Garnett and Pierce were traded to the Nets along with reserve Jason Terry during the summer.
"I left Boston?" Pierce said when asked of James' comments, clearly noting he had been dealt by the Celtics and didn't leave as a free agent.
Garnett and Pierce were both critical of Allen after he elected to sign with the Heat last offseason. KG said he lost Allen's phone number, and Pierce said he hadn't forgiven him.
"I think the first thing I thought was, 'Wow, Ray got killed for leaving Boston, and now these guys are leaving Boston,'" James said. "I think it's OK; I didn't mind it. But there were a couple guys who basically [expletive] on Ray for leaving, and now they're leaving.
"That's the nature of our business, man. I don't know what Boston was going through at the end of the day. I know Ray had to make the best decision for him and his family and his career. Doc [Rivers, former Celtics coach], KG and Paul did that as well. You can't criticize someone who does something that's best for their family."
James, of course, left the Cleveland Cavaliers to sign with the Heat in 2010. His "decision" remains infamous to this day.
"I can relate to that -- you think so? I'm the No. 1 relater," James said. "I've been through it all. I know all about it."
Information from ESPN.com's Brian Windhorst was used in this report.