The 33-year-old had hoped to stay at Craven Cottage but the club was unwilling to improve the offered terms, which were deemed unsatisfactory.
Willian, whose current deal expires tonight, has already begun opened talks with top-flight rivals as he looks to remain in English football.
The Brazil international’s decision comes as a huge blow for the Cottagers, who reaped the rewards of bringing Willian back to these shores last season.
Manager Marco Silva was also keen to keep Willian but is now left seeking replacements.
Silva's own future is not fully secure and a recent change of agents raised fears over a possible exit. There is a belief, however, that he will snub lucrative offers from clubs in Saudi Arabia to remain at Fulham.
The former Watford manager has one year remaining on his contract, which has a £6m release clause.
Shakhtar Donetsk loanee Manor Solomon could also leave the club with Tottenham interested in hijacking their free transfer bid.
Spurs play a friendly against Shakhtar this summer, hinting at a potential decision by the Israel international.
