This study indicated the relevance of performing molecular analysis to determine the most clinically important blood group systems, including Rh (D, C, c, E, and e), Kell (K, k, Kpa, and Kpb), Kidd (Jka and Jkb), and Duffy (Fya and Fyb) in Iranian alloimmunized transfusion‐dependent thalassemia patients. The gene discussed is RHCE; the disease is thalassemia.