Leishmaniases are considered serious public health problems, and their geographical expansion has enabled their establishment in urban areas of medium and large cities in Brazil. Continuous processes of deforestation, construction of dams, and hydroelectric plants, among others, cause environmental impact and may favor the increase in the number of human cases of leishmaniases, as well as the establishment of epidemic outbreaks. This scenario reflects the reality of some regions of Brazil, such as Tocantins State, which in recent years has recorded high levels of American visceral leishmaniasis (AVL). This study is aimed to analyze environmental and epidemiological factors related with the spatial and temporal distribution of AVL and with the occurrence of Lutzomyia (Lutzomyia) longipalpis, the main vector of AVL, in the state of Tocantins. The results indicate that the vector is adapted to all environments, especially the ones under human influence, and that anthropogenic environmental impacts can support the development and adaptation of AVL in Brazil. Such information could be applied in control strategies aimed at decreasing AVL incidence.