The 24-year-old Bender's existing deal had been due to expire in June 2017 and the club backed by pharmaceutical giant Bayer opted to extend his contract to ward off potential suitors such as Bayern Munich, who made an approach last summer.
"Lars Bender has come on leaps and bounds at Bayer 04 and now plays for Germany as a full international," managing director Michael Schade said on the club's official website. "He is a key player in our team and also an absolute top hit with the Werkself fans."
"Our team is strong and has the potential to improve even further," Bender said, whose twin brother Sven plays for Borussia Dortmund and has also been capped at full international level. "I want to be part of that story and make my own contribution to ensuring we can become an obvious and permanent member of the leading group."