Tettey, who plays in defensive midfield, has signed a two-year contract with the Canaries with the option of an extra year.
The Ghanaian-born player began his career at Rosenborg before moving to Rennes after six years in Norway.
Tettey then spent three years in France, making 82 appearances for Rennes before his move to Carrow Road.
Manager believes that the 26-year-old - the club's seventh signing of the summer - has the experience to prove a valuable asset.
"I'm delighted to have Alexander on board and I firmly believe he will be a valuable asset for us," he said.
"He's a very good player with international experience, and he's at a good age for us."
Tettey will not be able to play in tomorrow's match against Queens Park Rangers, but could feature in their League Cup second-round tie against Scunthorpe on Tuesday.