Joe Schmidt was rushed to hospital and had his appendix removed straight after Ireland's 26-23 victory over Australia in Dublin on Saturday.
Ireland's head coach delayed medical attention to guide his side to their first autumn Test series clean sweep in eight years, before being rushed to St Vincent's Hospital.
The former schoolteacher was admitted and underwent surgery on Saturday night and is now recuperating, the Irish Rugby Football Union (IRFU) has confirmed.
"Following yesterday's game against Australia, Ireland head coach Joe Schmidt was assessed by the match-day doctors and was sent to St Vincent's Hospital for further assessment," read an IRFU statement.
"On Saturday night Joe had his appendix removed and is recovering well this morning.
"Joe would like to thank the doctors and nurses of St Vincent's Hospital and everyone for their well wishes and kind messages of support."
Former Leinster boss Schmidt kept his counsel over his illness on Saturday despite his condition apparently worsening throughout the day.
Simon Zebo and Tommy Bowe claimed tries while Johnny Sexton booted 16 points to secure Ireland's seventh consecutive victory, Nick Phipps' brace and a further score for Bernard Foley not enough for the Wallabies.
Ireland assistant coach Les Kiss said boss Schmidt had "toughed out the day" in typically understated fashion.
"He had some pretty bad stomach pains through the day," said Kiss. "He toughed out the day in true Joe style."
Ireland captain Paul O'Connell said without prior knowledge no one would have realised Schmidt was battling a nasty illness.
"Guys were aware he was sick, he was kind of stand-off-ish, he was worried about passing on anything he had," said O'Connell.
"If you hadn't have been told, I don't think anyone would have known."