Foreigners visiting Iran are required to follow local dress code:

WOMEN should have their heads and bodies covered (arms down to wrists and legs down to ankles) everywhere, apart from the privacy of their own hotel room. It doesn't mean, though, that women are restricted to full chador. We recommend to wear loose trousers and a manteau or a long shirt covering heaps. Hair must be covered with either a scarf or a hijab. Nevertheless, it is acceptable to have some locks of hair to be visible from under the cover. Women in Iran wear multi-coloured clothes and scarves, there is no need to prepare only dark and black clothes when you pack for your trip to Iran. If some mosques require female visitors to be fully covered, our guides will have chadors prepared for the whole group.

Clothes for MEN have less restrictions: the only item not acceptable in Iranian society is shorts. Men can wear T-shirts everywhere. Nevertheless we suggest to bring several long-sleeved shirt for mosques visits. You will see young locals wearing T-shirts there as well, but to cover arms for men in a religious institutions is more responsible.