Background: Toxoplasma gondii and Neospora caninum are protozoans infecting a wide range of mammals; the etiologic agents of Toxoplasmosis and Neosporosis respectively, This study investigated the prevalence of antibodies to Toxoplasma gondii and Neospora caninum in dogs from southwestern Nigeria. Materials and Methods: A total of 233 serum samples were obtained from both urban and rural areas of Oyo state, Nigeria and tested by the western blotting technique for specific IgG to T. gondii and N. caninum. Results: The seroprevalence obtained for T. gondii was 19% (44/233) and 2.1% (5/233) for N. caninum in the dogs examined. Overall, the prevalence of antibodies to T. gondii was more significant than for N. caninum (P< 0.0001). T. gondii infection was also found to be more significant in roaming than in caged dogs (P< 0.05). There was no significant association of other factors (age, breed, history of rabies vaccination, use of dog and the level of education of owner) with the prevalence of T. gondii and N. caninum infection. Conclusion: This report revealed that T. gondii infection is more common than N. caninum infection in Nigerian dogs, it suggests that improper housing and feeding of dogs could increase the risk of exposure to T. gondii infection. This is the first study to investigate the seroprevalence of N. caninum antibodies in Nigerian dogs and T. gondii antibodies in dogs in southwestern Nigeria.