The 32-year-old joined the club in 2015 from German side Hamburg for £2.5m and has gone on to make 49 appearances in all competitions for the 'Hornets'.
Behrami started 26 Premier League games last season for Watford, but is is understood that he does not feature in Marco Silva's plans for the coming season.
Silva has already signed Will Hughes and Nathaniel Chalobah from Derby County and Chelsea respectively and competition in the Waford engine room is expected to be fierce this season.
Speaking after Watford's 0-0 draw with Aston Villa on Saturday, Silva said: "Valon is working on the training ground but he's one player who won't stay with us."
"It's time for him to find other solutions for his career, and we will see where he will play, but he will not stay in our squad."
The Switzerland international has been linked with a return to his homeland with FC Sion, though there is also interest from Italy, where the player has spent much of his career.