The 25-year-old signed a four-year contract, after completing his medical examinations.
Djedje has been speaking to French newspaper L’Equipe, before leaving for Austria to join his news teammates for pre-season training.
He explained the reason for choosing Watford, despite having offers from other clubs.
“I had other proposals, yes, even a German club, but I preferred to sign for Watford because this is a good club. I will find some former players of Ligue 1 and because it allows me to set foot in the Premier League.”
The Ivorian international revealed he had a chat with Swansea forward Andre Ayew before signing for Watford, and that Walter Mazzarri wanted to sign him at Napoli.
He added: “I spoke with Andre Ayew but didn’t tell him exactly where I was going to sign (he laughs).
“Clubs of the Big Four were already watching me when I was in France. I had discussed with the coach (Walter Mazzarri), who also wanted me to sign when he was at Napoli (2009 to 2013).
“I feel with him I can continue to progress. He wants to play his 3-5-2 team, this is a system that suits me well because we played in a slightly similar way with Marcelo (Bielsa).”