Tzolis, buldged the net 16 times with 10 assists across 46 appearances in all competitions last season for PAOK.
The 19-year-old played a part of Poak's Greek Cup triumph as they also finished second in the domestic league.
"I would like to thank everyone for the very good welcome. I'm very happy to be a part of this team and I hope to see the fans as fast as possible.
"I spoke with the coach [Daniel Farke] and he told me the plan and what he will do with me in the team. It's a very good project for me to sign here.
"From the first moment, I was really excited to come here. I said to my agent to sign as fast as possible here. It's a very good step for me.
"[Last year] was my first professional season. I had good stats and we won the cup in Greece. It was a very good season for me and I hope to continue like this here in the Premier League."
Having signed for Norwich, Tzolis joins his Greece team-mate Dimitris Giannoulis at the Canaries
Norwich boss Daniel Farke also added;
"We are all delighted with this signing. There was a lot of interest in Christos from some of the biggest teams in Europe.
"In his age group, Christos is probably one of the most exciting offensive players across European football.
"He's a young winger with lots of pace and potential. He's in a good physical condition and has been there delivering with many goals and assists for a big club in Greece in PAOK.
"Of course, we will give him the time to improve and adapt to English football, but we have a player with a lot of potential and a great personality."
Tzolis who has eight Greece caps, made his first international debut last October.
