In the third extension of the voting time, the Iranian Interior Ministry has extended the deadline to 2200 local time (1730 GMT).
The ministry said in a statement that voters can continue to cast their ballots until 2200 local time on Friday, four hours beyond the initial 10-hour deadline.
Polls officially opened across Iran at 8:00 a.m. (0330 GMT) and were originally scheduled to end at 6 p.m. (1330 GMT).
The country's Election Headquarters, meanwhile, said there had been no report of major irregularities from the polling stations, where representatives of the candidates have been stationed for more transparency.
Nearly 50.5 million Iranians, including more than 1.6 million first-time voters, are eligible to vote in the June 14 elections.