There is a lack of epidemiological data on Toxoplasma gondii infection in dogs from eastern China. In the present study, serum samples from 288 dogs were collected from Xuzhou, Huaiyin, and Yianchen in Jiangsu Province, eastern China, in August 2010; T. gondii antibodies were assayed by a modified agglutination test (MAT). Antibodies to T. gondii were found in 62 of 288 (21.5%) with MAT titers of 1∶25 in 21 dogs, 1∶50 in 15, 1∶100 in 11, 1∶200 in 6, and 1∶400 and above in 3 dogs. The seroprevalence in ≥3-yr-old dogs was significantly higher (P < 0.05) than that in dogs less than 3-yr-old. The results of the present study indicated that infection with T. gondii in household dogs in Jiangsu Province is a public health concern.