While human illness associated with hantavirus infection has been documented in many countries of South America, evidence for hantavirus transmission in Peru has been limited to the isolation of Rio Mamore virus from a pigmy mouse rat (Oligoryzomys microtis) in the Amazon city of Iquitos. To address the possibility of human hantavirus exposure in the region, we screened febrile patients reporting to health clinics in Iquitos from 2007 to 2010 for serological evidence of recent hantavirus infection. In addition, we conducted a serological survey for hantavirus-reactive IgG among healthy participants residing in Iquitos and rural areas surrounding the city. Through the febrile surveillance study, we identified 15 participants (0.3%; 15/5174) with IgM reactive to hantavirus (Andes virus) antigen, all with relatively mild, self-limited illness. From the cross-sectional serosurvey we found that 1.7% (36/2063) of residents of the Iquitos area had serum IgG reactive to one or more hantaviruses, with a higher prevalence in the urban population (2.2%, compared to 1.1% in rural areas). These results suggest that human infection with hantavirus has occurred in Peru.