In recent years, surveys of Toxoplasma gondii infection in dogs have been reported throughout the world, including China. However, information is lacking regarding the prevalence of T. gondii infection in pet dogs in northeastern China. In the present study, we report the seroprevalence of T. gondii in pet dogs in Shenyang, northeastern China. Sera samples from 328 pet dogs in 5 districts were examined for T. gondii antibodies with an indirect hemagglutination antibody (IHA) test; 10.0% tested seropositive. There were no significant differences in terms of sex, age, and locality (P > 0.05). The results indicate that infection by T. gondii is widely prevalent in pet dogs in Shenyang, northeastern China, which has potential implications for public health in this area.