The Turkey international agreed to move to the Merseyside outfit in August but struggled to tie down a regular starting spot in Brendan Rodgers’ first-team.
The 24-year-old made just 12 appearances, with central-midfielders Joe Allen, Steven Gerrard, Jordan Henderson and Lucas Leiva all providing Sahin with competition.
He was part of the Dortmund side which won the Bundesliga title in 2011, and he expressed his delight to rejoin Jürgen Klopp’s side until the end of the campaign.
“I am delighted to be back home,” he said. “My contact with the bosses, the players and the coaching team of Dortmund has never broken down over these last 18 months.
“I hope that I can help the team as soon as possible.”
Dortmund’s general manager Hans-Joachim Watzke is confident Sahin will add depth to the squad with Klopp’s men fighting on three fronts this season.
“We emphasised during our title celebrations in 2011 that Nuri Sahin will always remain a very special Borussia Dortmund player and that the door would always be open to him if he ever felt the desire to come back and play for us,” he said.
“In the past few days, Nuri approached us with this wish, and we have made it become reality.
“We are very pleased to be able to welcome another player of his quality to our squad.”
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