The Hoops boss had already recruited defender Efe Ambrose from Ashdod as well as bringing in Getafe forward Nicolas Fedor - known as Miku - and Nantes goalkeeper Lubos Kamenar on loan.
Nouioui, 26, who spent the last three years with Spanish side Deportivo La Coruna, is looking forward to playing for Celtic in the Champions League where they will come up against Barcelona, Benfica and Spartak Moscow.
"I'm absolutely delighted to sign for Celtic," he told the club's official website. "Celtic is a huge club with a magnificent history and a fantastic support. I know all about the wonderful atmosphere at Celtic Park and I can't wait to play there.
"I know that Celtic already has a great squad of players and I'm very much looking forward to joining up with my team-mates. I hope to play my part in bringing success to the club and, of course, I'm also looking to competing in the UEFA Champions League with such a great football club."
Lennon, who is looking for Nouioui to "bring another dimension to the team", is hoping the international break will allow some of his injured players to recover.
Kris Commons' ankle problem meant he started on the bench and when midfielder Victor Wanyama was replaced by debutant Jackson Irvine for the start of the second-half after the Kenyan could not overcome a dead leg, he teamed up with fellow youngster Filip Twardzik in the middle of the park.
Lennon said: "It's taken its toll on the squad. We had so many players out and we lost Victor at half-time. He has had a dead leg for quite a while, it is not majorly serious but there's no doubt we missed him because we had two rookies in centre of midfield.
"They did fine. Filip has been there or thereabouts for a while and Jackson made his debut. Hopefully after this two-week break when we go to St Johnstone we will have a good squad to pick from."