Essien, who has 58 caps at international level, is formerly of Lyon, Chelsea and Real Madrid, and it is with the Blues where he made his name. 256 appearances brought two Premier League titles, three FA Cups and a Champions League medal.
He first departed Stamford Bridge on loan in 2013, to sign for Real Madrid, before leaving on a permanent deal to Milan in January 2014.
His contract expires this summer, and the report claims Watford are tracking the Premier League veteran to add experience to their recently promoted squad.
Essien still has a house in London, and is said to be keen on a return to the Premier League, although wage demands could potentially infringe upon a potential move to Vicarage Road.
Essien was once arguably the best all-round midfielder in the Premier League, although injuries have done much to stall his career. He is still just 32, but it is hard to judge whether his body can now cope with the physical demands of the Premier League.