In the present study, we intended to determine the most clinically important antigens of Rh (D, C, c, E, and e), Kell (K, k, Kpa, and Kpb), Kidd (Jka and Jkb), and Duffy (Fya and Fyb) blood group systems by molecular assays and compare the blood group molecular genotyping with traditional serological phenotyping in alloimmunized multi‐transfused thalassemia patients who are at significant risk of making additional RBC alloantibodies. This evidence concerns the gene KEL and thalassemia.