Dengue viruses (DENV) are currently responsible for more human morbidity and mortality than any other known arbovirus, and all four DENV are known to exist in sylvatic cycles that might allow these viruses to persist if the urban (Aedes aegypti) cycle could be controlled. To determine whether DENV were being maintained in a sylvatic cycle in a forested area about 14 km southwest of Iquitos, Peru, a city in which all 4 serotypes of DENV circulate, we placed 20 DENV seronegative Aotus monkeys in cages either in the canopy or near ground level for a total of 125.6 months. Despite capturing >66,000 mosquitoes in traps that collected some of the mosquitoes attracted to these monkeys, blood samples obtained once a month from each animal were tested and found to be negative by an enzyme-linked immunosorbent assay for IgM and IgG antibodies to dengue, yellow fever, Venezuelan equine encephalitis, Oropouche, and Mayaro viruses. Although all four DENV serotypes were endemic in nearby Iquitos, the findings of this study did not support a DENV sylvatic maintenance and transmission cycle in a selected area of the Amazon rainforest in northeastern Peru.