Daryl Janmaat has secured his move to Watford from Newcastle United on a four-year deal for a transfer fee of £7m.
Sky sources reported earlier on Wednesday that the 27-year-old Netherlands international right-back was heading to the Hornets for his medical.
Janmaat signed for the Magpies in a £5m deal from Feyenoord in 2014 and made 78 appearances.
He has also played 27 times for the Dutch national team, including five games at the 2014 World Cup in Brazil, since making his international debut four years ago.
The versatile defender has played twice in the Championship this season, against Fulham and Huddersfield, but was left out of the squad for Tuesday night's EFL Cup clash at home to Cheltenham.
He told the club's website: "I'm really happy to be here, it's a new adventure for me. I was really pleased that Watford showed interest in me because I wanted to play in the Premier League.
"We [Newcastle] lost three times to Watford last season. They had a good season and I hope we can do the same again this year.
"The club is showing great ambition and wants to improve and I want to be part of that."
Newcastle manager Rafa Benitez said on Monday that the club could sell Janmaat if they received a "fantastic offer" for the player.
Benitez also said: "I told him the other day that, if he is here, he is a player that I like. He is a good professional and I don't have any problem."
Janmaat began his career at Heerenveen before a 2012 move and a two-year spell with Feyenoord.
Watford host Arsenal in the Premier League on Saturday, having drawn at Southampton and lost at home to Chelsea in their two games thus far.