The club also released an official statement on the stock exchange confirming that talks with Chelsea are going ahead.
The statement read: “Talks with Chelsea and Marko Marin are underway.”
Turkish clubs listed on the stock exchange must disclose negotiations to the public before announcing the completion of a transfer.
Clubs often release a statement confirming talks as a formality before announcing the transfer.
Marin arrived at Trabzon airport on a private jet today and was greeted by Trabzonspor fans who presented the 26-year-old with a team scarf.
The Germany international will become the second former Chelsea player at Trabzonspor following the transfer of Jose Bosingwa.
Former Blues players Samuel Eto’o, Gökhan Töre, Raul Meireles and Ricardo Quaresma also play in the league while Kenneth Omeruo is on loan from Chelsea at Kasımpaşa.
Trabzonspor have won both league games this season and take on Akhisar next at the Avni Aker.