A 25-year-old man was found dead at his computer at 7 am on Saturday in the eastern city of Suzhou, Jiangsu province.
He had been watching a World Cup group match between Chile and Australia, the official provincial news website reported.
A former football player also died from a heart attack in the north-eastern city of Shenyang on Saturday after watching a later game between Spain and the Netherlands, the Shenyang Evening Newsreported.
During the group stages, the World Cup matches take place at midnight, 3 am and 6 am Beijing time.