Leoz's lawyer, Ricardo Preda, told The Associated Press his client died Wednesday after a cardiac arrest linked to age-related ailments.
Leoz, under house arrest for the last four years, was indicted in 2015 in the US Justice Department's sweeping investigation of bribery and financial corruption linked to broadcasting and sponsorship rights for soccer competitions, including the Copa Libertadores.
South American soccer body CONMEBOL announced Leoz's death on Twitter. Leoz had served as president of the Paraguay-based organization from 1986-2013.
One of Leoz's achievements as CONMEBOL president was to gain diplomatic immunity for its headquarters in Asunción as protection from prosecution.
Leoz resigned from CONMEBOL and his FIFA executive committee seat in 2013 before the FIFA ethics committee could punish him following long-standing allegations he took kickbacks from World Cup revenues.
Leoz received hundreds of thousands of dollars from Swiss-based marketing agency ISL, which was selling World Cup television rights. ISL's collapse into bankruptcy in 2001 provoked a financial crisis for FIFA and led to a criminal trial in Switzerland.