Iranian nationality law contains principles of both jus sanguinis

Jus sanguinis

Ius sanguinis is a social policy by which citizenship is not determined by place of birth, but by having a parent who are citizens of the nation...

and jus soli

Jus soli

Jus soli , also known as birthright citizenship, is a right by which nationality or citizenship can be recognized to any individual born in the territory of the related state...

. Children acquire nationality of Iran

Iran

Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

 through their fathers, but not their mothers. The full nationality law is defined in Book 2 of the Civil Code of Iran, Articles 976 through 991.

Definition of Iranian nationals

Article 976 of the Civil Code of Iran defines who is an Iranian national:

1. All persons residing in Iran except those whose foreign nationality is established; the foreign nationality of such persons is considered to be established if their documents of nationality have not been objected to by the Iranian Government.
2. Those born in Iran or outside whose fathers are Iranian.
3. Those born in Iran of unknown parentage.
4. Persons born in Iran of foreign parents, one of whom was also born in Iran.
5. Persons born in Iran of a father of foreign nationality who have resided at least one more year in Iran immediately after reaching the full age of 18; in other cases their naturalization
   Naturalization
   Naturalization is the acquisition of citizenship and nationality by somebody who was not a citizen of that country at the time of birth....
   
    as Iranian subjects will be subject to the stipulations for Iranian naturalization laid down by the law.
6. Every woman of foreign nationality who marries an Iranian husband.
7. Every foreign national who has obtained Iranian nationality.

Multiple citizenship

Article 977 of the Civil Code of Iran deals with multiple citizenship

Multiple citizenship

Multiple citizenship is a status in which a person is concurrently regarded as a citizen under the laws of more than one state. Multiple citizenships exist because different countries use different, and not necessarily mutually exclusive, citizenship requirements...

. As a consequence of Paragraphs 4 or 5 of Article 976, some Iranian minors may have multiple citizenship. If they wish to retain the non-Iranian nationality after age 18, they have to inform Iran's Ministry of Foreign Affairs

Ministry of Foreign Affairs (Iran)

The Ministry of Foreign Affairs is an Iranian government ministry. The Minister for Foreign Affairs is the Cabinet member in charge....

.