In the capital Berlin, AK Party supporters celebrated in Turkish-populated neighborhoods, such as Kruezberg, by singing songs and waving flags and banners.
In Kurfurstendamm, one of Berlin's most famous avenues, Erdoğan's supporters made themselves heard in a large convoy of cars, chanting slogans and honking their car horns.
Celebrations also took place in other cities, including Cologne and Frankfurt.
Erdoğan is currently leading in the presidential runoff with 53.41% of the vote, while opposition candidate Kemal Kılıçdaroğlu has 46.59%, with 75.42% of the votes counted, according to the Supreme Election Council (YSK).
On May 14, no candidate won the required 50% in the first round, thus triggering a presidential runoff, although the incumbent Erdoğan took the lead with 49.52%.
More than 64.1 million Turkish citizens were registered to vote, including over 1.92 million who earlier cast their ballots at overseas polling stations.
