The 40-year-old singer was scheduled to perform with Dead & Company on Dec. 5 in New Orleans.
John Mayer was rushed to the hospital for emergency appendectomy on Tuesday, ET can confirm.
Dead & Company, which consists of Grateful Dead's Mickey Hart, Bill Kreutzmann and Bob Weir, also announced the news via Twitter. Mayer was scheduled to perform with them on Tuesday in New Orleans, along with Oteil Burbridge and Jeff Chimenti. The show is now being postponed for a later date.
"All tickets for the December 5 show will be honored for the rescheduled date," another post on Dead & Company's Twitter page reads. "Information on the rescheduled date will be announced as soon as possible. Should ticketholders choose to seek a refund, they will be available at point of purchase."
Mayer recently performed with Dead & Company over the weekend in Austin, Texas. Following the postponed New Orleans show, they are also scheduled to play at the Amway Center in Orlando, Florida, on Dec. 7, and the BB&T Center in Sunrise, Florida, on Dec. 8.
No word yet on whether Mayer will be able to join them for the rest of the tour, which wraps Feb. 18 in Riviera Maya, Mexico.