Background: Hemolytic transfusion reactions are a major complication in patients with beta-thalassemia major receiving regular transfusions. These reactions can be influenced by blood group incompatibilities, particularly in settings with limited genotyping practices. In Indonesia, the role of blood group genotyping in predicting hemolysis has not been thoroughly studied. Objective: This study aims to analyze the association between blood group genotyping and the incidence of hemolysis in people with thalassemia undergoing repeated transfusions. Methods: This is a cross-sectional study involving people with beta-thalassemia major younger than 18 years old who received regular transfusion with intervals of 2-4 weeks and have received more than 20 units of transfusion. Participants with leukemia, lymphoproliferative diseases, diabetes, solid tumors, and immunosuppression disorders were excluded from the study. Genotyping examination was conducted using Allele-Specific polymerase chain reaction (PCR ASP) while phenotyping was examined using immunoserology. Follow-up gene sequencing was conducted to observe the blood group variants. Hemolysis was assessed using several markers such as haptoglobin, free hemoglobin, lactate dehydrogenase, bilirubin, and hemoglobinuria, measured by Cobas Results: Clinical and laboratory data collection is completed. A total of 90 samples were collected, data analyses were undertaken, Conclusions: The results of this study will provide information on the blood groups' systems that can predict hemolysis occurrence in patients with beta-thalassemia undergoing repeated transfusion. These data will contribute to the best possible patient care management and blood transfusion therapy, thereby reducing the risk of hemolysis and improving the quality of life for International Registered Report Identifier (IRRID): RR1-10.2196/64379