Objective: To determine the association between reasons for blood donor rejection and transfusion safety in patients at Hospital III-Iquitos-EsSalud, 2021 2023. Material and methods: An analytical, longitudinal, retrospective study was conducted, including 9,614 applicants, including both eligible and rejected donors, as well as 4,430 transfused patients. The data were processed and analyzed using SPSS v. 25 and Epi Info statistical software. Frequency calculations and the chi-square test were performed. Results: The most common reasons for rejection were eosinophilia (18.71 %), low hemoglobin (16.57 %), and positive serology (12.72 %). The analysis of reasons for donor rejection associated with transfusion adverse events found a chi-square value of 1.969 with 1 degree of freedom and p=0.05, so the alternative hypothesis was rejected. Conclusion: The main reasons for donor rejection are ...