The 26-year-old, who joined Stuttgart from Bayern Munich in 2009, still had 18 months left to go on his previous deal, but has accepted the club's offer of a contract until 2016.
"I have established myself in the Bundesliga with Stuttgart and the club has a place in my heart," said the defender on vfb.de.
"I would like to grow even more as a leading player and play in Europe with this club.
"I will continue to give all I have got to achieve that in the coming years."
Stuttgart's director of sport, Fredi Bobic, welcomed Niedermeier's decision, saying: "We have managed to tie down another key member of our squad on a long-term deal.
"Georg is a guy whose passion and determination is infectious, which is why he is immensely important to our team."