This study aimed to clarify the effects of gardening on hemodynamic response, rating of perceived exertion (RPE) during exercise, and body weight in patients in whom phase 2 cardiac rehabilitation (CR) was interrupted due to the Coronavirus disease 2019 (COVID-19) pandemic. Among 76 outpatients participating in consecutive phase 2 CR in both periods from March to April and June to July 2020, which were before and after CR interruption, respectively, at Sanda City Hospital were enrolled. The inclusion criterion was outpatients whose CR was interrupted due to COVID-19. Patients under the age of 65 were excluded. We compared the data of hemodynamic response and RPE during exercise on the last day before interruption and the first day after interruption when aerobic exercise was performed at the same exercise intensity in the gardener group and the non-gardener group. Forty-one patients were enrolled in the final analysis. After CR interruption, the gardener group did not show any significant difference in all items, whereas the non-gardener group experienced significant increase in HR (Peak) (p = 0.004) and worsening of the Borg scale scores for both dyspnea and lower extremity fatigue (p = 0.039 and p = 0.009, respectively). Older phase 2 CR patients engaged in gardening did not show any deterioration in hemodynamic response or RPE during exercise, despite CR interruption and refraining from going outside. Gardening may be recommended as one of the activities that can maintain or improve physical function in older phase 2 CR patients during the COVID-19 pandemic.