Genotype 5 of hepatitis C virus (HCV) has been rarely identified in South America. A female of African descent who never left Brazil was found to be infected by this genotype in Mato Grosso state, Central Brazil. The patient denied drug injections and revealed that she had received blood transfusions several years before. One of her blood donors was identified and tested negative for anti-HCV and HCV RNA, as were her husband and offspring. Phylogenetic analysis of the E1 and NS5B regions confirmed that this HCV strain belonged to genotype 5a. However, the E1 region analysis indicates that our strain is not closely related to any sequences of genotype 5a from other geographical areas, diverging from the African and European subclades known so far. These data suggest that genotype 5a HCV might have been circulating at a low level in Brazil longer than previously supposed.