The 24-year-old, who spoke to reporters at a press conference on Monday, found the back of the net 20 times in 41 games for Sporting Lisbon last season.
"I'm glad to be here and can't wait to get started. This is the perfect move for me," the Dutchman told reporters.
"I had two great years at Sporting and I think I did a really good job there and did those fans proud.
"All the Dutch players that have played in the Premier League told me that this was the league to be in. Of course I can [score goals]. There is nothing more important for me."
Norwich reportedly had to part with £8.5m to secure his services this summer.