The 54-year-old has been out of work since being sacked by Inter in November 2014 but is expected to sign a three-year deal with the Premier League club.
Walter Mazzarri is set to become Watford’s new manager on a three-year contract, Goalunderstands.
Watford confirmed on Friday morning that Quique Sanchez Flores will be leaving the clubafter their final game of the season against Sunderland on Sunday.
Flores, who joined Watford last June, has managed to comfortably guide the club to safety in their first season back in the Premier League.
Former Napoli coach Mazzarri has been out of work since being sacked by Inter in November 2014.
In his first season at Inter, Mazzarri secured a fifth-placed finish in Serie A, but a poor start to the following campaign led to him being replaced by Roberto Mancini.
Mazzarri was more successful during his four seasons at Napoli where he won the Coppa Italia in 2012 and finished second behind Juventus in Serie A in 2013.