Dozens of police cars and minibuses converged on the capital's main squares on Monday during the early evening rush-hour. The "plan to increase security in society" - which began in Tehran but will extend nationwide - comes after an April crackdown resulted in thousands of warnings and hundreds of arrests.
The campaign would target women who were badly veiled, wore overly tight overcoats, sported excessively short trousers and were "dressed like models", a police spokesman, Mehdi Ahmadi, said. "As far as men are concerned we will act against those who have Western-style haircuts and clothing. We are also going to act against clothes shops and hairdressers."
He said 100 policewomen were among the officers sent to confront offenders. Those who infringed the law would be warned at first, then if necessary arrested and taken for "consultation".
"Normally the problem is resolved here," Mr Ahmadi said. "If not, and these cases are often those of reoffenders, the case is sent to the judiciary."
In Vanak Square, central Tehran, women were escorted towards a minibus by policewomen. They waited in the bus as the operation continued.
Other women were seen quickly adjusting their headscarves to cover loose hair.
Women in Iran are obliged to cover all bodily contours and their heads, but many have pushed the boundaries by showing off bare ankles and fashionably styled hair beneath their scarves.
Although the April crackdown was the severest such drive in years, some women are still donning figure-hugging coats and skimpy scarves. The wacky hairdos favoured by some young men in Tehran are also much in evidence.
Many conservatives have applauded the crackdown for protecting the security of society, but moderates have asked whether Iran would be better off tackling poverty and crime.
The city's police chief, Ahmad Reza Radan, said addicts, hooligans and sexual harassment in the street would also be targeted.
"Some young people, intentionally or unwittingly, are walking advertisements for Western deviant sexual and Satan-worshipping cults," he told the ISNA news agency.
"In this plan such people will be identified and confronted."