Studies conducted on free-ranging mithuns of Nagaland, India revealed that the overall seroprevalence of antibodies to Toxoplasma gondii in mithun was 42% (95% CI = 33–51) when detected by modified direct agglutination test. Highest (prevalence = 57%, 95% CI = 43–71) seroprevalence was found in mithuns above 3 years of age and the lowest (prevalence = 18%, 95% CI =4–32) in mithuns of 1–2 years old. No statistically significant difference was observed between male (prevalence = 40%, 95% CI = 26–54) and female (prevalence = 44%, 95% CI = 31–57) seroprevalences. The study also revealed that the maximum number (57%) of animals with the highest titre (1 : 3200) were above 3 years of age. This is the first serological survey for Toxoplasma gondii antibodies in free-ranging mithuns from India.