The 24-year old playmaker joined the Reds on a season-long loan from Real Madrid in the summer but after failing to fire at Anfield, has been sent to former club Dortmund.
"Sahin arrived at Anfield for a season-long stay in August 2012, but will now spend the rest of the campaign with Borussia Dortmund, the side with whom he won the 2011 German championship," read a statement on Liverpool's official website.
Sahin, who has rejoined Dortmund on loan until the summer of 2014, said: "I am happy to be home again.
"My contact with the club officials, players and coaches never stopped in the past year and a half. I hope I can quickly help the team."