Toprak, who signed for the outfit in 2011 from Freiburg, said that he was looking to win trophies in the future and believes that it is possible to do so with the players at the club.
"I'm really pleased that we've agreed on this long cooperation," Bundesliga.com quotes Toprak as saying. "Bayer 04 have placed a lot of faith in me in these few years, but that is not the only reason why I feel so happy in Leverkusen.
"We've got a strong team with which we can achieve our lofty ambitions. That is why it was such an easy decision for me to commit to the club until 2018."
Toprak has been capped 19 times by Turkey.