The Your Body Is A Wonderland singer was due to perform at a concert with the Dead & Company in New Orleans on Tuesday but was postponed.
Mayer is yet to comment publicly on his emergency surgery.
The band didn't provide any further details on Mayer's condition or how the procedure went.
John Mayer had to undergo an emergency appendectomy in New Orleans on Tuesday (December 5), representatives said.More news: Emergency protective order issued against OU running back Rodney Anderson
A statement from a Dead & Company rep adds, "All tickets for the December 5 show will be honored for the rescheduled date".
However, as you can imagine the show that John Mayer was supposed to show up at in New Orleans tonight has been postponed indefinitely while he remains in the doctors' care.
Ticketholders can also seek a refund at point of purchase, according to the band's social media account.
This story is still developing...
Bob Weir tweeted a photo with his bandmate, captioning it, "Wishing a speedy recovery for John".