Dog ownership has been associated with increased physical activity in the general adult population. The objective of this study was to examine dog ownership and dog walking and their relationship with home-based and phase II cardiac rehabilitation exercise, depression, and hopelessness in patients with ischemic heart disease. A total of 122 patients with ischemic heart disease were included in this prospective observational study. Patients completed dog ownership/walking questions during their hospitalization. The Cardiac Rehabilitation Exercise Participation Tool, Patient Health Questionnaire-9, and State-Trait Hopelessness Scale were completed by mail at 3, 8, or 12 months later. Regression modeling was used to evaluate the significance of dog ownership/walking on exercise, depression and hopelessness. The sample was 34.4% female and had a mean age of 64.7 ± 9.1 years. Forty-two patients (34.4%) reported owning a dog. Patients who owned but did not walk their dog reported significantly lower levels of home exercise compared with patients who walked their dogs at least 1 day per week (36.8% for non-dog walkers vs 73.9% for dog walkers, P = .019). The odds of participating in home exercise were significantly higher for dog walkers compared with non-dog walkers (odds ratio, 8.1 [1.7, 38.5] vs 1.0). There were no differences in phase II cardiac rehabilitation exercise, depression, or hopelessness between dog owners and non-dog owners or between dog walkers and non-dog walkers. These findings show a beneficial effect on home-based exercise for those who dog-walk at least 1 day per week. Healthcare professionals should encourage dog walking to increase dog owners' physical activity levels.