In this study, a horticultural therapy program was performed by employing the anger experienced by people during daily life activities in the emotion regulation strategy-based program to identify the influence of the horticultural program on anger control in the caregivers for patients with dementia. To measure this influence, two tools were used: a self-administered questionnaire survey, which is a subjective test, and an instrumental test, which can measure the physical index that detects the physical changes through anger. For the preliminary test, depression, stress, self-esteem, anxiety, and anger state-characteristic were tested using the self-administered questionnaire. For the follow-up test, the self-administered survey and the test using the physical index were performed in a manner similar to that of the preliminary test. The self-administered questionnaire comprised questions suitable to this study and considered the age, education level, and economic aspect of the subjects. The test results indicated that the experimental group subjected to the emotion regulation strategy-based horticultural therapy showed very significant reduction in depression and anger and significant reduction in stress, self-esteem, and anxiety. In the physical index test, the systolic and diastolic blood pressures were reduced, and the pulse rate and respiration rate reduced before and after the therapy, thus, proving the effectiveness of the therapy in anger control.