The singer, who left the rock group in 1979, will replace current frontman Bernie Shaw as he recovers from a routine medical procedure.
Lawton was already preparing to hit the high notes with his former bandmates this summer (13) as a special guest at a festival show in Spain in July (13), when he was billed to perform alongside Shaw. That concert is still scheduled to go ahead.
Uriah Heep founder and guitarist Mick Box tells Blabbermouth.net, "I am delighted to welcome back my old mate to the band. With Bernie off duty for a short while, John was the most obvious choice... I knew that his pipes (vocals) were in great shape, and that he would also be accepted readily by the Heep fans.
"All credit to John, though, as once he had heard of the problem and was asked, he re-arranged a lot of his schedule to fit in with ours, which was really cool!
"This will be a special set of dates with John, as we will be playing some classic songs in this nostalgic set, that may never be repeated."