The 27-year-old has joined the Premier League champions from Hannover for an undisclosed fee.
Zieler made more than 200 appearances for Hannover and has six Germany caps to his name after making his international debut in 2011.
"It feels great coming to Leicester and joining the club after they've had such a great season," Zieler told Foxes Player. "It's really nice to be part of the club now.
"I've been shown around the training ground and it looks very good and I've been to the stadium. I heard about the great atmosphere and the great fans, so my first impression is very good."
Zieler, who was in Joachim Low's squad for Germany's World Cup win in Brazil 2014, spent two years at Manchester United and a loan spell at Northampton Town.