BACKGROUND: It is well known that malaria can be transmitted via blood transfusion. However,it is not documented in the national donor screening protocol. Magnitude of asymptomatic malaria among donors would be the key to decide on the need of donor screening. Despite this, there is lack of such data in Ethiopia. The aim of this study was thus to estimate the prevalence of asymptomatic malaria and associated factors among blood donors.METHODS:An institution basedcross-sectional study was conducted in Arba Minch blood bank from February to June, 2015. Data was collected from donors who passed the clinical donor selection criteria and recruited by systematic random sampling technique. A structured questionnaire was used to capture data on socio-demographic characteristics. Giemsa stainedblood films were examined for plasmodium parasites. Magnitude of asymptomatic malaria was calculated and association of factors with malaria was assessed by multivariable logistic regressions using SPSS version 20.0.RESULTS: A total of 416 donors participated in the study. The proportion of infected donors was 4.1% (17/416). Eight donors were infected with Plasmodium falciparum while 9 donors were infected with Plasmodium vivax. Most positive blood films (13/17) were with parasite loads ranging from 100 - 500 parasites/µl. Donors with blood group O were more susceptible to malaria parasitemia compared to all other ABO blood groups together (AOR=6.899, 95%CI=1.951-24.391, p=0.003).CONCLUSION: Magnitude of malaria parasitemia in the present study was high as compared to the national malaria prevalence. Hence, in malaria endemic areas of Ethiopia, blood should be screened before donation. KEYWORDS: Blood transfusion, malaria prevalence, blood donor