AbstractBackgroundBrazil has a high prevalence of arboviruses, especially Dengue (DENV), Zika (ZKV), and Chikungunya (CHKV).ObjectivesTo study the risk of DENV, ZKV, and CHKV transmission by blood components in the haematopoietic stem cell transplantation (HSCT) population.MethodsProspective cohort of HSCT recipients and donors performed at the Hospital das Clinicas da FMUSP, São Paulo‐Brazil. Patients were evaluated by serology and RT‐PCR for DENV, ZKV, and CHKV pre‐transplantation and once a week until neutrophil grafting. In positive cases (positive RT‐PCR and/or serology conversion), an investigation was carried out on the blood components that the patient received to evaluate the possibility of it being transfusion transmitted.ResultsA total of 93 patients were included during the study period. The mean age was 52 years with a predominance of males (56.9%). We considered five (5.3%) DENV cases positive by seroconversion in our study. One patient had IgM seroconversion and the other four presented IgG seroconversion to DENV. In the investigation of the blood components, 145 individual samples were analysed. None of the investigated blood components showed a positive RT‐PCR.ConclusionWe observed a low prevalence of DENV, ZKV, and CHKV in HSCT donors and recipients by serology and RT‐PCR, and no case of blood transfusion transmission by RT‐PCR.