Iranian President Hassan Rouhani's allies have won all of the capital's 30 seats in parliament, with 90 per cent of votes counted from last week's election, state television reported on Sunday.
The pro-Rouhani List of Hope, led by reformist Mohammad Reza Aref, a former vice president, knocked the number one conservative candidate, Gholam-Ali Hadad Adel, into 31st place, sealing a whitewash, according to the preliminary results.
The tally showed Hadad Adel more than 6,000 votes behind the candidate in 30th place with the remaining 10 per cent of ballots to be counted.
The results were based on around 2.6 million votes from a total of 2,900,000 in the capital, a key battleground.
Should the results be confirmed, it would also mean that all eight women on the List of Hope would be elected.
A total of 290 seats were up for grabs in Friday's election.
In the 260 seats in the provinces, the president's allies fared less well.
Out of the 56 constituencies outside the capital, 19 went to the main list of conservatives, nine to the pro-Rouhani list and 14 to independent candidates.
Of the independents, six had ties to conservatives, five to reformists and three were undeclared.
None of the remaining 14 seats had a clear winner, meaning a second round of voting will be needed, which is not expected until April or May.