Holland international Janmaat, who joined Newcastle in July 2014 from Feyenoord, has signed a four-year contract at Vicarage Road
The 27-year-old said in quotes reported on watfordfc.com: "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."
Janmaat made 77 appearances in all competitions for Newcastle, scoring four goals
His final outing for the Magpies came in a 2-1 home defeat at the hands of Huddersfield Town earlier this month
Source : PA
Source: PA