The pair are likely to fight for one starting spot under Mauricio Pochettino.
The move finally addresses fan concern over the cover the club have up top for Harry Kane.
Vincent Janssen scores the first goal for Netherlands
But with Spurs boss Mauricio Pochettino favouring one up top, and Kane coming off the back of two great seasons, Janssen may find himself on the bench often.
But, speaking to De Telegraaf after completing his move, he made it clear this was of no concern:
"Of course I want to play football. But I will need time to adapt.
“However, I know there will be plenty of minutes. With the Premier League, Champions League, FA Cup and League Cup Spurs played a lot of matches.
“I'm going to enjoy all the playing time I get. "
England's Harry Kane
Last season Spurs spent the whole campaign with Kane as essentially their only out-and-out striker – after the departures of Roberto Soldado and Emmanuel Adebayor.
Janssen’s arrival will no doubt alleviate some of the pressure on their main man Kane – who looked burnt out at the Euros for England, putting in several poor performances.
England's Harry Kane looks dejected
Tottenham have plenty of football to play next season and Pochettino is keen on rotating the squad when he can.
But it will be interesting to see who wins the battle to be the number one striker when it comes to the big games.