Toxoplasmosis is a zoonosis caused by Toxoplasma gondii, which infects almost all mammals and birds. Felids are definitive hosts that shed oocysts of T. gondii with their feces, which is then transmitted by oral ingestion. The study analyzed the prevalence of T. gondii infection in free-ranging cats on Tokunoshima Island, Kagoshima Prefecture from 2017 to 2018, and found a seropositivity rate of 47.2% (59/125). This result indicated the importance of understanding and managing the behavioral patterns of felids, including the free-ranging cats. Toxoplasmosis is also an important food-borne parasitic disease due to its ability to be transmitted by consuming undercooked meat of infected animals. Considering that all developmental stages of T. gondii, including oocyst, tachyzoite, and cysts, are capable of infection, a One Health approach that considers the health maintenance of humans, animals, and the environment is important for the control of toxoplasmosis.