Nationality as a legal, political, and spiritual phenomenon is not immutable and can be acquired in various ways. One way of acquiring nationality is through marriage of an individual with a citizen of another state, and states have taken different positions on this issue. The present article seeks to conduct a comparative study of the acquisition of nationality by marriage in international documents, the legal systems of the Iran and Türkiye. The present article, in examining the main question of how to acquire citizenship through marriage in international documents, the Iranian legal system, and the Turkish legal system through the application of the comparative method has found that, in international documents, system of independence has been accepted, which is particularly manifested in the "Convention on Certain Questions Relating to the Conflict of Nationality Laws"(1930), the "Convention on the Nationality of Married Women"(1957) and the "Convention on the Elimination of All Forms of Discrimination against Women"(1979). In Iranian law, two systems of unity and relative independence are accepted, but in the Turkish law, the system of independence prevails. According to international documents and Turkish law, in which the system of independence is accepted, the principle is that marriage does not have an automatic and consequential effect on nationality.Considering that equality is not necessarily the same as justice, the combined application of the two systems is considered more appropriate. Avoiding efforts to achieve formal equality and applying methods in an integrated manner can better lead to the realization of justice and family-centeredness.