Objectives: This study investigates the psychological and physiological effects of a smart garden on psychiatric patients attending a day ward in a mental hospital. Methods: A one-group pretest-posttest design was applied for this study. Twenty-four patients admitted to a mental hospital in ChunCheon City were included in the study and participated in a mindfulness meditation program in a cute-type indoor garden. The smart garden program was provided to the participants twice a week for 4 weeks, 10 minutes per session. A Self-Report Scale (SRS) and heart rate variability (HRV) of the patient were collected before and after experiencing the entire smart garden program. The SRS included three segments: Beck’s Depression Inventory (BDI), Beck’s Anxiety Inventory (BAI), and the World Health Organization Quality of Life Brief Version (WHOQOL-BREF). Furthermore, the patients’ HRV was assessed based on six parameters: standard deviation of the N-N intervals, square root of mean squared difference of successive N-N intervals (RMSSD), total power (TP), high-frequency, low-frequency, and low-frequency/ high-frequency ratio. Results: After attending the smart garden program, a significant difference emerged in three test areas in the SRS (BDI, BAI, and in the physical health domain of the WHOQOL-BREF; p<0.01), and in two HRV parameters (RMSSD and TP; p<0.05). Conclusion: Results of the subjective and objective evaluation tools revealed that exposure to a smart garden program provides relaxing psychological and physiological effects to psychiatric patients.