Janssen's 27 league goals in 34 appearances for AZ Alkmaar last season saw a number of Premier League clubs take interest in his signature, including Manchester United and West Ham.
But the 22-year-old admitted that he had quickly made a connection with the Spurs manager which made his choice an easy one.
"After the tour of the training ground and [White Hart Lane], I knew for sure that this is a fantastic club," Janssen told De Telegraaf.
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"To be honest, [the fee] doesn't affect me - I do not feel any pressure.
"Of course I want to play football.
"But I will need time to adapt.
"Yet I know there will be plenty of minutes.
"With the Premier League, Champions League, FA Cup and League Cup I will play many games with Spurs.
"And I'm going to enjoy all the playing time I get."