Objectives Increased physical activity predicts survival and reduces risk of readmission in patients with coronary heart disease. However, few data show how physical activity is associated with survival and readmission after heart valve surgery. Objective were to assess the association between physical activity levels 6-12 months after heart valve surgery and (1) survival, (2) hospital readmission 18-24 months after surgery and (3) participation in exercise-based cardiac rehabilitation. Methods Prospective cohort study with registry data from The CopenHeart survey, The Danish National Patient Register and The Danish Civil Registration System of 742 eligible patients. Physical activity was quantified with the International Physical Activity Questionnaire and analysed using Kaplan-Meier analysis and Cox regression and logistic regression methods. Results Patients with a moderate to high physical activity level had a reduced risk of mortality (3 deaths in 289 patients, 1%) compared with those with a low physical activity level (13 deaths in 235 patients, 5.5%) with a fully adjusted HR of 0.19 (95% CI 0.05 to 0.70). In contrast, physical activity level was not associated with the risk of hospital readmission. Patients who participated in exercise-based cardiac rehabilitation (n=297) were more likely than the non-participants (n=200) to have a moderate or high physical activity level than a low physical activity level (fully adjusted OR: 1.52, 95% CI 1.03 to 2.24). Conclusions Moderate to high levels of physical activity after heart valve surgery are positively associated with higher survival rates and participation in cardiac rehabilitation.