The meaning of acquired citizenship is that type of citizenship that is given to a person after birth, which can be achieved either forcibly or voluntarily. In the present study, the methods of acquiring citizenship in Iran and France and the challenges and gaps in acquiring acquired citizenship in the two mentioned countries have been discussed with the approach of the principles governing citizenship and existing laws in both countries. The results of the research show that the citizenship status of the children of Iranian women married to foreign men is ambiguous in the Iranian legal system, but this problem does not exist in the French legal system due to the transfer of citizenship to these children through the French mother. In the Iranian legal system, imposing the citizenship of a foreign woman In case of marrying an Iranian man, citizenship is given due to the unity of the family, but in France, the independence of the citizenship of the couple is established, dual citizenship is accepted in France, but the Iranian legal system is silent on this matter. Regarding the citizenship of adopted children and refugees and the applicant's language and cultural and social information, French laws are more complete than Iranian laws, but there is a gap in Iran's legal system regarding the mentioned cases.