Before the Friday prayers, Turkish President Recep Tayyip Erdoğan recited from the Quran inside the reopened mosque, choosing from both the Surah Al-Fatihah and the Surah Al-Baqarah.
Later, four muezzins from the mosque's four minarets recited the adhan, or call to the prayer, and the people started the Friday prayers.
Besides being a working mosque, Hagia Sophia is also among Turkey's top tourism destinations for domestic and foreign visitors.
In 1985, during its time as a museum, Hagia Sophia was added to the UNESCO World Heritage List.
It served as a church for 916 years until the conquest of Istanbul, and a mosque from 1453 to 1934-nearly 500 years-and most recently as a museum for 86 years.
Erdoğan and other Turkish leaders had long advocated its restoration to a working mosque, open for worship.
On July 10, a Turkish court annulled a 1934 Cabinet decree that turned Hagia Sophia into a museum, paving the way for its use as a mosque.
In the new era for Hagia Sophia, Turkey's Religious Affairs Directorate oversees religious services at the mosque, while the Culture and Tourism Ministry supervises restoration and conservation work.
The architectural treasure is also open to domestic and foreign tourists free of charge.
