An outbreak of febrile illness was reported from January to February 2018 in the Expedito Ribeiro Settlement, Santa Bárbara do Pará municipality, Pará State, Brazil. This study aimed to investigate the pathogenic agent responsible for the outbreak and the circulation of arboviruses in the region. We analyzed 94 individuals through laboratory tests for arboviruses. Forty out of 94 individuals were asymptomatic but were living with or near febrile cases, and 55 participants were symptomatic. Our results showed that 51.1% of the investigated individuals were positive for arboviruses (Oropouche, Mayaro, and Chikungunya), of which 77.8% were symptomatic. We detected 93.7% of positive cases for Oropouche infection, 2.1% for Mayaro fever, and 4.2% were positive for both Oropouche and Chikungunya infection. Oropouche virus was mainly responsible for the outbreak; however, we also detected a few Chikungunya and Mayaro fever cases. Serologic assays showed evidence of arboviruses circulation of different genera in the area.