Canine visceral leishmaniasis (CVL) is a serious zoonotic disease in Brazil and Southern Europe. CVL is primarily caused by Leishmania infantum and its diagnosis relies largely on detection of parasites in bone marrow or lymph node aspirates by microscopic observation of the parasites in stained smears, parasite culture, or polymerase chain reaction (PCR). Serological tests exist but they do not distinguish active disease from simple exposure to parasite antigens. Here, we have assessed the utility of a new monoclonal antibody--based antigen (protein) detection test for the diagnosis of CVL. The test was positive in 70% of beagle dogs experimentally infected with L. infantum. In contrast, culture of the parasites from bone marrow aspirates was positive in only 40% of the infected animals. These preliminary results suggest that this antigen detection test, which we have recently described for the diagnosis of human VL, has the potential to be a useful diagnostic tool for CVL.