On 14 January 2013, Liverpool announced that they had in agreement with all parties terminated the loan agreement with Real Madrid and Şahin, and that this would now allow Şahin to join Borussia Dortmund on loan until the end of the 2013–14 season. Şahin spoke about the deal saying, "I realised that as a footballer and a human being, I belong here 100 per cent." Şahin also said "I noticed quickly that I only want to play for Dortmund." His return move delighted manager Jürgen Klopp. Prior his debut in the friendly match against Mainz, in which Dortmund won on penalties, Şahin said he was quite nervous for his return. Eight days later, he made his first league appearance, since leaving Dortmund, coming on as a substitute in a later minute, as Dortmund defeated Werder Bremen 5–0. On 16 March 2013, Şahin scored two goals in a 5–1 Dortmund victory over SC Freiburg.