Toxoplasma gondii infections are ubiquitous in both animals and humans. Although seroprevalence data exist for pet dogs across multiple Chinese provinces, limited epidemiological information is available for T. gondii infection in pet dogs in subtropical China’s Hunan Province. We examined T. gondii antibodies in pet dogs from Hunan Province using the indirect hemagglutination test. Logistic regression analyses were used to identify factors associated with T. gondii infection (season, sex, age, breed, and location). The overall seroprevalence was 10.8% (95% confidence interval (CI)=9.0–12.6) (118/1,092), with regional variations ranging from 8.0% (95% CI=4.2–11.8) to 21.1% (95% CI=8.1–34.0). Antibody titers followed a descending distribution: 42.3% (1:64), 30.5% (1:128), 20.3% (1:256), 5.1% (1:512), and 1.7% (1:1,024). The multivariate analysis identified the season (highest in summer: odds ratio=2.0, 95% CI=1.2–3.4) and age (>3 years: odds ratio=2.8, 95% CI=1.5–5.3) as factors independently associated with the outcome (P<0.05). These finding revealed the high seroprevalence of T. gondii infection in pet dogs in Hunan Province, subtropical China, highlighting the risk of zoonotic transmission. Therefore, effective measures should be taken to prevent and control toxoplasmosis in pet dogs in this province.