Janmaat is excited about his move to the Premier League and told Newcastle's official website: "This is a fantastic club, with a big history and a great stadium. I have also been told all about how great the fans are. This is the perfect move for me, and I am really looking forward to being with the team and getting started here at Newcastle. I think we are going to have a great season."
Magpies boss Alan Pardew added: "We are delighted to bring Daryl to the club. He is the perfect example of a modern full-back, someone who is good defensively but offers a real threat going forward as well.
"Daryl had an excellent World Cup and we are looking forward to him continuing that form for Newcastle."