The recent development of interferon-free regimens based on direct-acting antivirals for the treatment of chronic hepatitis C virus infection has benefited many but not all patients. Some patients still experience treatment failure, possibly attributed to unknown host and viral factors, such as IFNL3 gene polymorphism. The present study assessed the prevalence of rs12979860-CC, rs12979860-CT, and rs12979860-TT genotypes of the IFNL3 gene, and its relationship with ancestry informative markers in 949 adult Brazilian healthy blood donors. Race was analyzed using ancestry informative markers as a surrogate for ancestry. IFNL3 gene was genotyped using the ABI TaqMan single nucleotide polymorphisms genotyping assays. The overall frequency of rs12979860-CC genotype was 36.9%. The contribution of African ancestry was significantly higher among donors from the northeast region in relation to southeast donors, whereas the influence of European ancestry was significantly higher in southeast donors. Donors with rs12979860-CC and rs12979860-CT genotypes had similar ancestry background. The contribution of African ancestry was higher among rs12979860-TT genotype donors in comparison to both rs12979860-CC and rs12979860-CT genotypes. The prevalence of rs12979860-CC genotype is similar to that found in the US, despite the Brazilian ancestry informative markers admixture. However, in terms of ancestry, rs12979860-CT genotype was much closer to rs12979860-CC individuals than to rs12979860-TT.