Aim: To determine the prevalence and molecular epidemiology of human sapovirus (SaV) in both wastewater and stool samples in a 3-year (2012–2014) surveillance study performed in Rio de Janeiro State, Brazil. Methods and Results: A total of 156 wastewater and 341 stool samples were analysed using quantitative real-time PCR. SaV was detected in 3 5% (12/341) in stool samples with virus load concentrations ranging from 104 to 109 genome copies per gram (gc g 1), and in 33 0% (51/156) wastewater samples, with range concentration varying from 104 to 106 gc l 1. Partial genome sequencing of wastewater and stool samples revealed the circulation of genotypes GI.1, GI.2, GI.6, GII.1 and GV.1. Conclusion: This study demonstrated the prevalence of human SaV in acute gastroenteritis (AGE) cases and revealed, for the first time, the environmental dissemination of those viruses in Brazil. Significance and Impact of the Study: SaV diagnosis should be considered in hospitalized children with AGE and the higher positive rate detection in environmental samples suggests that SaV infection could be underestimated or associated with asymptomatic cases.