Kemal Kilicdaroglu, the only candidate, received 990 votes out of 1,238 at a congress of his Republican People's Party (CHP), AFP reported on Sunday.
Kilicdaroglu, a 67-year-old former civil servant, has lost all the elections he has taken part in since he was chosen as head of the party for the first time in 2010, when he replaced former leader Deniz Baykal who was sunk by a sex tape scandal.
In the November 1 general elections, the CHP, garnered just 25 percent of the vote compared to 49 percent for Erdogan's Justice and Development Party (AKP), which won back the parliamentary majority it had lost five months earlier.
In a speech to the congress, Kilicdaroglu condemned Erdogan as a "type of dictator" who has trampled on freedoms in the country.
He also spoke out against the arrest last week of some 20 academics who signed a petition condemning a military crackdown in the Kurdish-dominated southeast.
The European Union Saturday condemned the arrests as an "extremely worrying development."