US Edition Chris Gregory, 30, shocked his family by belting out a version of Irish ballad Danny Boy from his hospital bed, even though he has never visited the country.
Greeting his wife Mary with "It's da broid', he continued to speak in the new accent for 30 minutes until his normal voice returned.
Mr Gregory's strange behaviour – apparently the result of a rare condition called Foreign Accent Syndrome – lifted the mood of the intensive care ward at Sheffield's Royal Hallamshire Hospital where he was recovering from surgery to correct a life-threatening blood vessel rupture in his brain.
"All the nurses were trying really hard not to laugh, and I was too. I just couldn't take it in at first, it seemed so comical, but it didn't matter at all because I'd been so worried about losing him altogether," Mrs Gregory, 36, told the Daily Mail.
"Chris's Yorkshire accent had vanished completely, and he was talking like an Irishman all the time.
"At one point he looked at me adoringly and said: 'You're da fabbest gal oi know! ' with a perfect Irish lilt in his voice.
"It sounded crazy, but I didn't care. It was just great to have him back in one piece after such a traumatic time."
She added: "It's not as if Chris has any Irish relatives. He's no connection with the country and he's never been there – that's what makes it all so strange."
Mr Gregory, a payroll officer, is now fully recovered after the 2007 operation but has no memory of his temporary brogue.
"I've told Mary that she should have videoed me. At least then I could have sat back and watched myself singing Danny Boy," he said.
Foreign Accent Syndrome, which was first identified during the Second World War, causes patients to speak differently after a brain injury. In 2006 a woman from Newcastle began talking in a Jamaican accent after waking up following a stroke.