Harold McDowell said that he was "dumbfounded" by the win but that his wife's health meant more than the money.
On Friday, doctors confirmed that his wife was cancer free, after multiple surgeries for liver cancer and hospital stays for colon cancer.
Then on Saturday afternoon he won $1m (£790,000) at a casino in Atlantic City.
Mr McDowell, 85, bet just $5 in a game of poker and hit a six-card royal straight flush of diamonds.
The casino, Borgata Hotel, said the odds had been just one in 20,348,320.
He was dealt the 10, queen and ace of diamonds. The dealer's hand was the nine, jack and king of diamonds.
The retired public works director told the New York Post that his wife had been with him but she had been even more shocked by his win than he was.
He said: "I happened to be playing next to my wife. I had my back to her.
Mr McDowell said he was "dumbfounded" by the win, saying he had "sat there like an idiot".
The casino has taken a cut of at least $200,000 in taxes, he said, but the news about his wife's health was more important to him than the money.
He told the Post: "It was better news that she's healthy - money isn't the most important thing."
When asked what he would do with the money, he said he would give most of it to his children but he and his wife might take a cruise.
"Our lives will probably stay pretty much the same," he said. "But it might get better for our children."