Erdogan joined millions of people at the bridge over the Bosphorous, which was renamed to honor the martyrs after the coup attempt.
The commemoration event began with the national anthem, followed by a recitation of the Quran.
Earlier, having gathered in Beylerbeyi, Cengelkoy, Altunizade and Kisikli districts of the Asian side of the city, people marched to the bridge amid tight security.
The bridge was closed by putschists on the night of the coup attempt and dozens people were killed on it.
Rallies named "democracy watches" will begin after midnight.
Later, Erdogan is scheduled to depart for Ankara, where he would address the parliament at 2.32 a.m. local time (1132GMT), the time the parliament was bombed on the night of the coup attempt.
Sunday's program will begin with a morning prayer at Ankara's Bestepe Millet Mosque, followed by the opening of the July 15 Martyrs' Monument at the presidential complex.
The Fetullah Terrorist Organization (FETO) and its U.S.-based leader Fetullah Gulen orchestrated the defeated coup of July 15, 2016, which left 250 people martyred and nearly 2,200 injured.
Ankara also accuses FETO of being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police and judiciary.