You Need to Dress Appropriately
Iran is an Islamic country, and as such you need to follow the Islamic dress code. Here are some things to keep in mind.
Women need to cover their arms, legs and head. This including a Hijab, loose long length shirt with long sleeves and pants.
Leggings or tight jeans are ok as long as your top is long and covers your bottom. When wearing pants, you need to be covered down to your ankles.
The most common way to cover your head is with a scarf. The local women wear bright colors and are very stylish with their clothing, so don’t think you need to wear all black.
Black is still worn a lot but not so much among the younger generation.
You can wear sandals. Some guesthouses and hostels will allow you to take your headscarf off on their premises but do check first.
Men aren’t allowed to wear shorts in public, so bring long, lightweight pants as the best option. T-shirts are fine to wear in public. Men can wear sandals too.
If you do wear inappropriate clothing it’s not the end of the world, and besides some angry looks from some of the older generation, you’ll probably just end up having a friendly local let you know what’s best to wear.