The aim of this study was to determine the seroprevalence, clinical and biochemical profile of Leishmania chagasi infection in dogs naturally infected and identify the phlebotominae fauna in an endemic area of São Luis Island. In this present study, 62 household mongrel dogs were sampled for antibodies anti-Leishmania. The seroprevalence was 51.61%. In the clinical evaluation, 36.68% dogs were symptomatic, 38.41% were oligosymptomatic and 26.13% were asymptomatic. The most frequent signs were onychogryphosis and lymphadenomegaly. In 29.41% animals were observed anemia. In the biochemical analysis hepatic function showed changes in relation to alaninoaminotransferase (ALT) and aspartato aminotransferase (AST). Urea values were higher than the references ones for canine specie. The following phlebotominae sandflies were identified: Lutzomyia longipalpis (86.9%), L. evandroi (9.6%), L. choti (2.1%), L. umbratilis (0.7%) e L. whitmani (0.7%).