Background of study: Beta thalassemia is one of the commonly inherited genetic disorders and public health problem in India. Though hemotransfusion is the primary option to manage beta thalassemia, it may be associated with occurrence of red cell alloimmunization. Aim / Objective: The purpose of this study is to determine the prevalence, types and factors determining the alloantibodies in thalassemic children. Research Methodology: This cross sectional study comprised of 74 children of south India receiving regular blood transfusions. Study subjects were screened for the presence and type of alloantibodies. The details regarding previous transfusions were also collected using a predesigned profoma. Results: The prevalence of alloantibodies was 9.46% in the study group. Alloantibodies were common in thalassemic children of more than 14 years, females, non-splenectomised children, who initiated the transfusion at the age of less than six months, with B and O blood group and those who had undergone more than 150 transfusions. Anti __ampersandsignndash; C and Anti-kell antibodies were the most prevalent antibodies in the study group. Conclusion: Since these alloantibodies are haemolytic, appropriate treatment and care is necessary especially in thalassemic children and new strategies should be implemented to cut short the occurrence of erythrocyte alloimmunization.