The 55-year-old confirmed the news in a tweet from his hospital bed at St George's in Tooting, London.
"As this is starting to get out- I'm in ICU of St George's having suffered heart attack. Thanks to the professionals who saved my life," he wrote.
In a later post, he joked: "I'm trying to work out whether nearly 5K of likes over the news I've had a heart attack is sympathy or schadenfreude."
Moore earned 64 caps for England from 1987 to 1995 and also turned out five times for the British and Irish Lions.