The two-day congress was being held at Bilkent University's Odeon exhibition center.
On the first day of the congress, the delegates elected the party chairman, while on the second, they will vote to elect 60 members of the party's assembly.
Kemal Kılıçdaroğlu, the head of CHP, was announced as the only candidate for the chairmanship.
Kılıçdaroğlu has been serving as the chairman of CHP since 2010. He took office at the 33rd regular congress, held after the resignation of Deniz Baykal, the former chairman.
Özlem Çerçioğlu, the mayor of the metropolitan municipality in the western Aydın province, was elected a council chairperson of the party.