With 44 per cent of votes counted the pro-Rouhani List of Hope was ahead in all but one seat in the capital, with the head of the rival conservative slate the only candidate blocking a complete rout.
The domination of Tehran was in marked contrast to earlier initial results across the country which showed seats split between the main conservative list, Rouhani's allies and independents.
The List of Hope's leader and number one candidate, Mohammad Reza Aref, a former vice president, was in first place in the Tehran ballot, after 1,293,000 votes, from 2,900,000, had been counted.
The head of the conservative list, Gholam-Ali Hadad Adel, a former parliament speaker, was placed seventh.
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Outside the top 30 positions that would earn seats in parliament, the last remaining reformist candidate was in 31st place with the rest of the conservative hopefuls behind him.
Turnout in the election was solid at around 60 per cent, slightly less than the 64 per cent of 2012.
A total of 4,844 candidates, about 10 per cent of whom are women, stood in the parliamentary election.