It has been proposed that the transmission of canine visceral leishmaniasis might involve the participation of mechanical vectors, including ticks of the family Ixodidae, in particular the brown dog tick Rhipicephalus sanguineus, and the cat flea Ctenocephalides felis felis. Here, the association between the infestation by R. sanguineus and C. felis felis and the occurrence of anti-Leishmania antibodies was evaluated in an observational case–control study of dogs living in a Brazilian endemic area for canine visceral leishmaniasis. Blood samples were taken once every three months for one year from 96 initially seronegative domestic dogs, and submitted to indirect immunofluorescence antibody assay. All dogs were evaluated for the presence of ticks and fleas, and the results were expressed qualitatively as infested or non-infested, irrespective of the intensity of infestation. At the end of follow-up, twenty dogs had turned seropositive, while 68 remained seronegative and 8 were excluded because of incomplete data. All the dogs were asymptomatic. The odds of infection was significantly greater (OR = 3.54, CI95% = 1.10–12.53) for dogs infested by C. felis felis compared to their non-infested counterparts. In contrast, the odds of infection showed no significance difference between non-infested and R. sanguineus-infested groups of dogs (OR = 0.31, CI95% = 0.03–1.52). This study provides further evidence for the potential role of C. felis felis in mechanically transmitting Leishmania among the canine population.