Background: Sickle cell hemoglobinopathy is a genetic disorder caused by the presence of hemoglobin S (HbS), γG-158 (C→T) polymorphism plays an important function in the disease severity of sickle cell anemia, The XmnI restriction site at -158 position of the γG-gene is associated with increased expression of the γG-globin gene and higher production of HbF, Previous studies have suggested that a variety of genetic determents influence different clinical phenotypes. The genetic variants that modulate HbF levels have a very strong impact on ameliorating the clinical phenotype.Aim: This study aims to associate between Xmn1 (…γG-158 C→T …) polymorphism and fetal hemoglobin level among Sudanese patients with SCA.Materials and methods: In this descriptive cross-sectional study 60 blood samples from diagnostic cases were analyzed using a Hematology analyzer (Sysmex KX21N), capillary electrophoresis (MINICAP), using “G-spin™ Total DNA Extraction Kit", PCR-RFLP techniques. Results: Patients with SCA were analyzed for Xmn1 polymorphism and association between this polymorphism and severity of SCA was evaluated, the presence of one XmnI (+/-) site CT 2% in SS patients compared with XmnI-/- site CC98% had shown difference regarding HbF level, thus the Polymorphic association was founded. Conclusion: In our descriptive cross-sectional study we concluded that the effect of the polymorphism on the Hb F level was established.