Upset with a line call in the tiebreaker, Lendl had a 10-minute argument with lineswoman Dana Loconto.
McEnroe won three of the next four points—all on Lendl errors—to close out the match.
"I loved it," McEnroe said. "Now I know what it is like. It was outstanding. I got to have some fun, talk to some people. Take some pictures. It was awesome. He melted down and I pulled it out."
In the semifinals, McEnroe beat Jimmy Connors 6-4, and Lendl topped Pat Cash 7-6 (9-7).
On Wednesday night, McEnroe beat Cash in the final in Nashville, Tenn.