Background: Patients with thalassemia major are clinically dependent on red blood cell (RBC) transfusions . Performing multiple transfusions increase the risk of transfusion-related complications including blood-borne infections, iron overload and also RBC alloimmunization .

Materials and Methods: This cross-sectional descriptive study was conducted on 70 thalassemia cases with regular blood transfusions. The serum samples were screened for the detection of the unexpected antibodies and the positive samples were subjected to antibody identification.

Results: Among 70 cases, 6 (8.6%) were identified as unexpected alloantibody three cases as Anti-K, one as Anti-E and another one as Anti-D. Coincidence of Anti D and Anti-E was detected in one case. Eighteen patients (25.7%) were splenectomized. No significant correlation was seen between the presence of alloantibody and age, sex, the time of first transfusion and spleen condition.

Conclusion: Considering that the most prevalent unexpected antibodies (8.6%) identified in this study were against the Kell and Rh system antigens, the evaluation of compatibility for antigens found can be recommended before the performing of transfusion. Therefore, this strategy may decrease the possibility of recipient immunization and production of the unexpected antibodies against donor RBCs.