Ministry spokesman Martin Schaefer said consular officials will visit Deniz Yucel, a reporter for German daily Die Welt, in an Istanbul-area prison tomorrow.
Yucel was one of many journalists swept up in the aftermath of last summer's failed coup in Turkey. He is accused of disseminating terrorist propaganda and inciting hatred, as well as being a German spy and associate of the outlawed PKK group.
Germany has dismissed the claims as absurd and has pushed for Yucel's release.
Germany has said that a half dozen of its citizens are being held in Turkey, which has been one of several issues recently causing raised tensions between the two NATO allies.
Germany is also pushing for access to another journalist, Mesale Tolu, a 33-year-old German citizen with Turkish roots who has been in custody for more than two weeks. But Schaefer said that is still being denied.