The 24-year-old is currently on loan at Liverpool from Real Madrid, but has failed to make an impact at Anfield.
He has been linked with a return to his old club, with Dortmund coach Jurgen Klopp admitting he had remained in contact with the Borussia academy product since he left in 2011.
The Westphalian club have announced a press conference will be held at 18:00 local time this evening, with reports claiming it is to announce Sahin's return.
Sahin was voted the Bundesliga's player of the year at the end of the 2010/11 season, when he inspired the club to their first Bundesliga title since 2002.
He left to join Real that summer, signing a contract until 2017 with the Madrid club, although he struggled to break into the first team and was loaned out to Liverpool in August.