Metabolic syndrome (MetS) is an established risk factor for cardiovascular diseases and mortality. Limited data are available on the prevalence of MetS and its association with exercise among breast cancer survivors. The present study included 1,696 breast cancer survivors from the Shanghai Breast Cancer Survival Study, a population-based prospective cohort study conducted between April 2002 and October 2011 in Shanghai, China. All women had a physical examination taken at study clinic approximately 60 months post-diagnosis. Exercise was assessed at approximately 6, 18, 36, and 60 months post-diagnosis. Information on medical history, tumor characteristics, cancer treatment, anthropometrics, and lifestyle was collected at study enrollment. Associations between exercise and MetS at 60 months post-diagnosis were evaluated with multivariable logistic regression models. The mean age of the study population was 56.68 at 60-month survey, and the mean follow-up since cancer diagnosis was 63.66 months. The prevalence of MetS using National Cholesterol Education Program Adult Treatment Panel III criteria at approximately 60 months after diagnosis was 33.14%. Among overweight and obesity breast cancer survivors (body mass index (BMI) ≥ 25 kg/m(2) at baseline), the prevalence was 55.18%. The most common type of exercise in this population was walking (45.40%) at baseline. Exercise participation between 6 and 60 months post-diagnosis was inversely associated with the prevalence of MetS with the adjusted odds ratio (OR) for exercise participation of ≥ 3.5 h/week (30 min/day) being 0.69 (95% confidence interval (CI) 0.48-0.98). In addition consistent exercise participation reduced the prevalence of MetS (adjusted OR 0.70 (95% CI 0.50-1.00). Associations of exercise with MetS were not modified by baseline waist circumference, BMI, comorbidity, baseline menopausal status, TNM stage, cancer treatment, or ER/PR status (p interactions > 0.05). Regular and persistent exercise after cancer diagnosis, even at low-to-moderate intensity level, decreases the prevalence of MetS among long-term breast cancer survivors.