Sven Bender will join twin brother Lars at Bayer Leverkusen, Borussia Dortmund have confirmed.
Bender - whose switch is subject to a medical - joined Dortmund from 1860 Munich in 2009 and made 224 appearances for the club, winning the Bundesliga and DFB-Pokal twice.
The 28-year-old has been capped seven times by Germany and will move to Leverkusen in a deal worth a reported EUR15million.
Fitness problems including torn ankle ligaments hindered Bender last season, restricting him to three Bundesliga starts, and he told Dortmund chief executive Hans-Joachim Watzke and sporting director Michael Zorc he felt the time was right for a fresh challenge.
"A few days ago, I approached Aki Watzke and Michael Zorc with a personal request to take a new challenge after eight years at BVB," he told Dortmund's official website.
"As a little boy, I always wanted to be on the pitch. Also due to injuries, I have unfortunately unfortunately not been able to be used by BVB regularly.
"I am very grateful that Borussia Dortmund has respected my will, despite their unconditional desire to keep me. I feel that as a great appreciation."
Watzke added: "We would have liked to see Sven Bender still in our team. On the other hand, he is a player who, like a few others with great achievements, has given a lot of himself to BVB.
"These merits naturally require us to listen more closely and respect his personal desire."
Leverkusen begin their domestic season with a trip to Karlsruhe in the DFB-Pokal before opening the Bundesliga campaign away to reigning champions Bayern Munich.
Bender's first reunion with Dortmund will come in December when Peter Bosz's side travel to the BayArena.