"I accept the election results," Ince said at a press conference at the CHP's headquarters in Ankara.
"There is no significant difference between the official ballot reports that our officials have shown us and the figures announced by the Supreme Board of Elections. And the differences that existed would not have changed the overall outcome," he was quoted by local media as saying.
However, he vowed to continue his political struggle and fight to "win all our citizens' good wishes."
Ince called on President Recep Tayyip Erdogan, who won the race, to be "the president of everyone" instead of acting as the head of the ruling Justice and Development Party.
He also said the CHP should get well ready for the upcoming local elections in March 2019.
The unofficial election results showed Ince received 30.6 percent of the votes in the presidential race, based on the results of 99.9 percent of ballots, while Erdogan won 52.6 percent of the votes.
Turks cast their votes on Sunday in presidential and parliamentary elections, as part of the transition from a parliamentary political system to an executive presidential one, which was approved in a referendum last year.