He was one of the pioneers, in the years 1886–1897, of the efforts for the return of the exiled Joachim III of Constantinople.

He was forced to resign from the throne on 25 October 1918, retiring to Kadıköy, where he died and was buried in December 1920.

Germanus V is the author of an encyclical published in 1920 as a milestone for the ecumenical movement.

He evokes the notion of a "fraternity of churches" to be created, a "blessed union" of the churches for which he invites different traditions to contribute by engaging in the joint study of the essential questions around the notion of meeting: 1.

It then lists eleven basic points as a working proposal for future collaboration between the churches; Willem Visser 't Hooft, first secretary of the WCC, that the "With its 1920 encyclical, Constantinople rang the bell of our assembling".