"We're very happy that he has chosen Borussia Dortmund," the club's sporting director Michael Zorc said in a statement, adding that Dortmund would pay the release clause in Witsel's Tianjin contract without revealing any financial details.
"Axel is a player with a great deal of international experience who has all the skills to shape BVB's central midfield: tactical understanding, tackling power, speed, and creativity," Zorc added.
Witsel began his career at Standard Liege and played for Portuguese side Benfica and Russia's Zenit St Petersburg before joining Tianjin in January last year.
"I'm totally happy and also proud to be allowed to play for BVB soon. After our first conversation, I did not have to think twice, because for me Borussia Dortmund is one of the best clubs on the continent," Witsel said.
(Reporting by Simon Jennings in Bengaluru, editing by Ed Osmond)
