According to TMZ, Mayer's rep confirmed that the singer was forced to undergo a last-minute appendectomy.
Dead and Company is next set to play Thursday in Orlando, Florida.
Apparently, all of the purchased tickets will still be honored at the postponed date that is yet to be announced. He joined the group in 2015, alongside Oteil Burbridge, Jeff Chimenti and former Grateful Dead members Bob Weir, Mickey Hart and Bill Kreutzmann.
The 40-year-old Mayer "was admitted into the hospital for an emergency appendectomy" early Tuesday, a representative said in a statement without further detail.
The "Your Body is a Wonderland" hitmaker is now on tour with the band - comprised of Grateful Dead founders Bill Kreutzmann and Bob Weir, along with Mickey Hart, who joined the band two years after its formation in 1967 - and at the time of writing, it is unknown whether the remaining dates of their 2017 tour will also have to be postponed.
No word yet on whether Mayer's condition will have an impact on that show.
Get well soon, John!