The 34-year-old was free, after leaving Brazil’s Corinthians when his contract expired at the end of last season.
And according to the newspaper “The Sun”, Willian signed his contract to join Fulham, after he was training at the club’s training headquarters in the past days.
The veteran Brazilian will add some much-needed experience in the Premier League, having won two titles in the competition during his seven-year stay at Chelsea.
Willian played 339 games with Chelsea and scored 63 goals, before moving to Arsenal, where he spent one season.
Fulham are having a busy day ahead of the transfer deadline, as they look to sign a number of players before the window closes.
And coach Marco Silva’s team is close to completing the procedures for the inclusion of former Tottenham striker Carlos Vinicius, in a deal worth 9.5 million pounds from Benfica.
Fulham is also interested in signing Paris Saint-Germain left-back Levin Kurzawa after Nice signed Joe Brien on loan.