The 31-year-old striker, who signed for Larissa in August, was rushed to hospital in the early hours of Monday morning but was pronounced dead on arrival at Larissa's University Hospital.
"The Larissa family mourns from today the tragic loss of 31-year-old international Mexican footballer, Antonio De Nigris," a club statement said.
"It is with deep sorrow that the administration, technical leadership, players and executives of the club would like to express their condolences to his family, particularly his spouse Sonia and five-year-old daughter Miranda."
"An autopsy will be held at the General Academic Hospital in Larissa to determine the precise reasons of his death."
De Nigris, who represented Mexico 16 times including at the 2001 Copa America, joined Larissa from Turkish club Ankaragucu and made six appearances in the Greek Super League.
