Objectives. To assess the entomological risk of Aedes aegypti in boats traversing border river routes in Loreto. Materials and Methods. The study population consisted of mosquitoes present in three boats covering border routes in Loreto. The entomological risk of Aedes was determined through ovitraps, the inspection of breeding sites, and the collection and taxonomic identification of adult mosquitoes. Results. The entomological risk varied according to the route and the season. A medium to very high entomological risk was identified in the high-water season and on the outward route to the border areas. The predominant vector population in the low-water season was Mansonia sp. (74.8%), Culex sp. (12.8%), and Aedes aegypti (0.4%); in the high-water season, Culex sp. (45.1%), Mansonia sp. (26.8%), and Aedes aegypti (19.7%). In no case did we find Aedes albopictus. Conclusions. There is moderate to high entomological risk during the high-water season in riverboats traveling from Iquitos to the border areas of Loreto. Our results show that river boats are a means of expansion of Aedes aegypti.