BVB have agreed to pay the Belgium international's release clause and it is expected the deal will be officially ratified over the coming days.
The move to Dortmund will be Witsel's first chance to play in one of the big five leagues in Europe, as he represented the likes of Benfica and Zenit Saint Petersburg before moving to China in January 2017.
The 29-year-old was one of the star performers for Belgium at this summer's World Cup, as he helped Roberto Martinez' side secure a third-place finish and he admits he has been keen to return to Europe since the finals concluded and Dortmund appears to be the right fit.
'After the World Cup, it was my goal to move from China back to Europe,' Witsel said. '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. Honestly, I cannot wait to run around in front of 81,000 people.'
Dortmund sporting director Michael Zorc is equally delighted by the imminent arrival of Witsel, as he feels the former Standard Liege star will thrive at Signal Iduna Park.
'We have been very interested in signing Axel Witsel for many months and are very happy that he has chosen Borussia Dortmund, Zorc said.
'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, creativity and mentality.'