The Metropolitan Police said objects had been thrown at police during the protest and that four officers had sustained minor injuries, though none were believed to have been taken to hospital.
The man who removed the flag was arrested on suspicion of criminal damage, trespass on diplomatic property and assaulting police, the Met said. He remains in custody.
The force added that a group of protesters had attempted to prevent his lawful arrest and dispersal tactics were used by officers “to ensure the safety of those concerned and prevent further disorder”.
A section 35 dispersal order was imposed outside the embassy “as a result of ongoing disorder”, it added.
A London Ambulance Service spokesperson said it was called to reports of an incident at the junction of Exhibition Road and Kensington Road – near where the Iranian embassy and a number of other embassies are located – at around 20:45 GMT on Friday.
Four people were taken to hospital while two others were treated at the scene, they added.
Earlier this week, the Iranian ambassador in London was summoned to the Foreign Office after a number of protesters in Iran were killed.
Last Saturday, two people were arrested at a protest outside the embassy in which a demonstrator also climbed onto the building’s balcony and appeared to tear down the Iranian flag.
