Swiss international Roman Buerki moved from relegated Freiburg to Dortmund, the BVB announced in an official statement.
The eight-time German champions made use of Buerki's release clause in the contract which runs until 2018, Xinhua reported.
The BVB on Sunday transferred 3.5 million Euros to sign Thomas Tuchel's desired candidate between the posts.
The 24-year-old goalkeeper made overall 34 Bundesliga appearances for Freiburg and two caps with the Switzerland national soccer team.
He will compete with goalkeeper veteran Roman Weidenfeller and Mitchell Langerak for the starting position in Dortmund's goal.
The BVB completed the last Bundesliga season on a disappointing 7th place of the standings and coach Juergen Klopp resigned after seven successful years with Dortmund.
Former Mainz coach Thomas Tuchel takes the helm officially on July 1 after putting pen to paper on a three-year deal, until June 2018.
