The 23-year-old left Panathinaikos last year to join the Serie A club on a free transfer but found it difficult to hold down a first team place and made only 14 appearances during a disappointing season.
"I am very happy to come to an environment where there are many Greek internationals, this counted a lot in my decision to move to PAOK, as well as the fact that the club pursued me," Ninis said.
"I wanted the next step in my career this year to be something solid and reliable and a place where I could adapt quickly."
Ninis, who has scored three goals in 23 matches for his country, will link up with fellow Greek internationals Kostas Katsouranis, Dimitris Salpigidis, Alexandros Tziolis, Nikos Spiropoulos and Stefanos Athanasiadis at PAOK.
- Sports & Recreation