Background/aim: Recurrent pregnancy loss (RPL) is defined as two or more pregnancy losses. T-regulatory cells play an important role in the feto-maternal interface. Cytotoxic-T-lymphocyte antigen-4 (CTLA-4) is a molecule that downregulates the activation and proliferation of T cells. The objective of the current study was to investigate the possible association of CTLA-4+49A/G gene polymorphism with RPL among patients from the Iranian Azeri Turkish ethnic group. Materials and methods: The study group/patients consisted of 101 women with the experience of two or more pregnancy losses and the control group consisted of 101 women with at least two live births, without any previous history of pregnancy loss and autoimmune diseases from the same ethnic group. The CTLA-4+49A/G was detected by polymerase chain reaction-restriction fragment length polymorphisms assay. Results: The distribution of CTLA-4+49A/G genotype was AA, 38.61%; AG, 51.48%; GG, 9.9% in patients and AA, 37.62%; AG, 47.52%; GG,14.85% in controls (P-value: 0.2). Furthermore, no association in G-allele was observed in the patient and control groups (P-value: 0.5). Conclusion: The results of the present study suggest that CTLA-4 does not have any association with RPL in the Iranian Azeri Turkish ethnic group.