The pair got a standing ovation when they teamed up at Elton’s Aids fundraiser White Tie and Tiara Ball.
Elton casually introduced George to join him for a rendition of Don’t Let The Sun Go Down On Me, the song they performed at Live Aid in 1985.
A guest told UK newspaper The Sun: “Everyone went mad – it was a special moment.”
The pair are said to have hardly spoken since 2004, when Elton said troubled George was “in a strange place”.
Elton performed a string of his hits at the bash, held at his home in Windsor, Berkshire.