Abstract Introduction Iran is host to one of the largest urban refugee populations worldwide, about two million of whom are undocumented immigrants (UIs). UIs are not eligible to enroll in the Iranian health insurance scheme and have to pay out-of-pocket to access most health services. This increases the likelihood that they will delay or defer seeking care, or incur substantial costs if they do seek care, resulting in worse health outcomes. This study aims to improve understanding of the financial barriers that UIs face in utilizing health services and provide policy options to ensure financial protection to enhance progress towards UHC in Iran. Methods This qualitative study was conducted in 2022. A triangulation approach, including interviews with key informants and comparing them with other informative sources to find out the complementary findings, was applied to increase data confirmability. Both purposive and snowball sampling approaches were used to select seventeen participants. The data analysis process was done based on the thematic content analysis approach. Results The findings were explained under two main themes: the financial challenges in accessing health services and the policy solutions to remove these financial barriers, with 12 subthemes. High out-of-pocket payments, high service prices for UIs, fragmented financial support, limited funding capacity, not freeing all PHC services, fear of deportation, and delayed referral are some of the barriers that UIs face in accessing health care. UIs can get insurance coverage by using innovative ways to get money, like peer financing and regional health insurance, and by using tools that make it easier, like monthly premiums without policies that cover the whole family. Conclusion The formation of a health insurance program for UIs in the current Iranian health insurance mechanism can significantly reduce management costs and, at the same time, facilitate risk pooling. Strengthening the governance of health care financing for UIs in the form of network governance may accelerate the inclusion of UIs in the UHC agenda in Iran. Specifically, it is necessary to enhance the role of developed and rich regional and international countries in financing health services for UIs.