Travel to Iran for US, UK, and Canadian citizens is legal.
The first advice for citizens of the three countries is to apply for their Iran visa 2-3 months before their trip.
Before applying for a visa , American, British, and Canadian travelers must obtain a travel authorization number from the Iranian Ministry of Foreign affair (MFA). In order to obtain the number form MFA the traveler must have an itinerary that will be given to him/her by an Iranian travel agency. The travel agency that is organizing your trip can help you with authorization number process. Once you have the number you can apply for your visa and you can choose which consulate or embassy you wish to pick up your visa from.
There are three choices for the travelers. First is to book a trip with a tour guide that gives you the opportunity to have a totally tailor made tour itinerary. It is just like solo traveling.
Second option to pay less for the travel is to book a small group tour. It is cheaper than traveling with a tour guide and you will have fellow travelers on your trip.
And the third is to book a tour with a bigger group that will be even cheaper and more people will accompany you during your Iran travel.
All the travelers including U.S, U.K, and Canadian citizens can enter all the seven Iran’s Free Trade, Industrial & Special Economic Zones (Kish and Qeshm Island, Chabahar, Aras, Anzali, Arvand, and Maku) without a visa.
Whether you are traveling with a private tour or a group tour you will be warmly welcomed by the Iranian officers at the gate.
The only occasion in which your admission to Iran will be denied is if you have Israel visa or stamp in your passport.
Another rule that Iran travelers must be informed of is the country’s dress code. Headscarf and loose clothing are mandatory for Iranian and tourist ladies. Gentlemen are required to wear long pants. You can read the details for dress code here.
Once the mentioned citizens are inside the country, everything is as normal as it is for other tourists. Despite what the western media is trying to show, Iran is a safe country for tourists. In fact, all Iran travelers enjoy the hospitality and warm welcomes from Iranians during their trip.