The 72-year-old Trinidadian is the former head of Caribbean and North and Central American football (Concacaf), but quit Fifa in 2011.
He is fighting extradition to the US on corruption charges and denies accepting millions of dollars in bribes.
Warner committed "many and various acts of misconduct continuously and repeatedly" said the football world governing body's ethics committee.
Fifa's ruling follows its own investigation into the bidding process for the 2018 and 2022 World Cups, which began looking at Warner's activities in January 2015.
On Tuesday, Fifa said Warner had been found guilty of violating the organisation's code of ethics several times.
A statement read: "In his positions as a football official, he was a key player in schemes involving the offer, acceptance, and receipt of undisclosed and illegal payments, as well as other money-making schemes."
The United States wants to try Warner and 13 other current or former Fifa officials who were indicted in May.
Prosecutors allege that Warner - who was one of football's most powerful figures whose support was seen as crucial for any World Cup host bid - has been involved in criminal corrupt practices for more than two decades.
In June 2015, a BBC investigation found evidence of bribes paid to Warner.