The arrests are part of an operation that has seen women targeted for posting photos showing them not wearing headscarves on Instagram and elsewhere.
Women in Iran have been required to cover their hair in public since 1979.
The eight unnamed people were among 170 identified by investigators as being involved in modelling online.
They included 59 photographers and make-up artists, 58 models and 51 fashion salon managers and designers, according to a statement from the court.
The arrests were announced by the court's prosecutor Javad Babaei during a state television programme broadcast late on Sunday that focused on the "threats to morality and the foundation of family" posed by social media.
Mr Babaei claimed modelling agencies accounted for about 20% of posts on Instagram from Iran and that they had been "making and spreading immoral and un-Islamic culture and promiscuity".
Of the 170 people found to be involved in online modelling, 29 were warned that they were subject to criminal investigation, the prosecutor added.
"The persons who reformed their behaviour after receiving a notice did not face any judicial action, and eight out of the 29 have been arrested," he said.
A spokesman of the Iranian Centre for Surveying and Combating Organised Cyber Crimes, Mostafa Alizadeh, said: "Sterilising popular cyberspaces is on our agenda.
"We carried out this plan in 2013 with Facebook, and now Instagram is the focus," he added, saying fresh operations would begin in the coming days.
There was no immediate comment from the photo-sharing site Instagram, which is owned by Facebook.

The Canadian, 28, was picked as the Devils' forward of the year in 2016-17 after scoring 24 goals and 29 assists in 66 games.
Haddad was a dominant force last season, playing the role of a power forward as Devils won the Elite League.
"Joey Haddad was outstanding for us last season," said Devils player-coach Andrew Lord.
"There were a number of games that he completely took over or broke open a game for us and that is what makes fans love him so much.
"He is a big body and dominates in the corners and is tough to play against.
"There were a number of teams that wanted him to make a move but he loves it here and I don't really think he entertained any other offers."
Haddad will also be a vital part of Devils' Champions Hockey League campaign, with the Welsh side drawn in Group E against HC Davos from Switzerland, Bili Tygri Liberec of the Czech Republic and Sweden's Vaxjo Lakers.

Dr Christopher Davies, who works for the the Royal Berkshire Hospital, said a matron later purchased the item for £22.95 from Homebase instead.
Dr Davies, a respiratory consultant, said it was then fitted for free by in-house staff.
A hospital spokesperson said the quote was reviewed and "firmly rejected".
Dr Davies said the blackout blind "must have been gold plated" to warrant such a price, the Mail on Sunday reported.
He wrote: "So many posts about inadequate funding but here's an example of how the money is used... maybe it's not just about poor funding."
In a statement issued to the BBC, the hospital said: "In line with NHS requirements, the trust sought quotes for a blind which meets fire and infection control regulations.
"This particular quotation was reviewed by the management team and firmly rejected."
NHS England has been approached for comment and said it was looking into the situation.

The sisters-in-law have been named as Sharon Dodd-Archibald, 46, and Mary Archibald, 51, both from Glasgow.
They were found at the flat in Dalserf Court in the Gallowgate area on Sunday.
Their deaths are not being treated as suspicious. Police are awaiting the results of toxicology tests and post mortem examinations.
Following the discovery of the women's bodies at about 12:00 on Sunday, police said that one line of inquiry was possible carbon monoxide poisoning.
Although police will not formally rule that out until a cause of death has been established, it has emerged that no faults were found with the boiler during tests carried out by the Health and Safety Executive and Scottish Gas.
There are no other gas appliances within the flat.
Iran has arrested eight people working for online modelling agencies deemed to be "un-Islamic", the prosecutor of Tehran's cybercrimes court has said.
[NEXT_CONCEPT]
Cardiff Devils attacker Joey Haddad has re-signed for a fourth season with the Elite League champions.
[NEXT_CONCEPT]
A senior doctor has spoken out after his hospital was quoted £855.80 for a blackout blind by its official NHS contractor.
[NEXT_CONCEPT]
The deaths of two women at a flat in Glasgow may not be due to gas poisoning after a boiler was found to be in working order with no faults.