Serum samples from 19 jaguars (Panthera onca), nine pumas (Puma concolor), and two ocelots (Leopardus pardalis) were collected between January 1999 and March of 2005 and tested for presence of canine distemper virus (CDV). All cats were free-ranging animals living in two protected areas in the Brazilian Atlantic Forest. In addition, 111 domestic dogs from nearby areas were sampled for CDV. Our results show the first evidence of CDV exposure in Brazilian free-ranging felids. From the 30 samples analyzed, six jaguars and one puma were tested seropositive for CDV. All seropositive large felids were from Ivinhema State Park, resulting in 31.5% of the sampled jaguars or 60% of the total jaguar population in Ivinhema State Park, and 11.28% of the sampled pumas. From the total 111 domestic dogs sampled, 45 were tested seropositive for CDV. At Morro do Diabo State Park, 34.6% of the dogs sampled were positive for CDV, and 100% at Ivinhema State Park. Canine distemper virus in wild felids seems to be related with home range use and in close association with domestic dogs living in nearby areas. © 2009 International Association for Ecology and Health.