Without identifying the person, the German foreign ministry said it could "confirm the unconditional release of a German citizen who had been jailed for political reasons in Turkey".
Turkey was however still holding seven German citizens "for political reasons" out of a total of 50 Germans behind bars in the country.
Berlin-Ankara ties have been badly strained, especially since Turkey's 2016 failed coup and subsequent crackdown, which Germany and other western nations have criticised as excessive.
Germany, home to a large Turkish minority, has since urged a cut in EU funding linked to Turkey's membership talks, which have ground to a virtual standstill.
President Recep Tayyip Erdogan, in an interview published Thursday, expressed hope for a better relationship with Germany and the EU after a fractious 2017.
His comments followed Turkey's recent release from months of detention of German pilgrim David Britsch and German journalist Mesale Tolu.
However the German-Turkish correspondent of Die Welt newspaper, Deniz Yucel, who was arrested in February, remains behind bars, and no date for his trial has been set.