Objectives: The purpose of this study was to report the short-term blood pressure-lowering effects observed in a patient with malignant hypertension through slow breathing maneuver with heart rate variability(HRV) biofeedback. Methods: Biofeedback sessions, totaling 13, each lasting 10 minutes, were administered. Blood pressure was measured pre and post-treatment, as well as thrice daily at 10 am, 4 pm, and 8 pm. Systolic blood pressure(SBP), diastolic blood pressure(DBP), and pulse rate were recorded for comparative analysis. Results: Before biofeedback, the average SBP, DBP, and pulse rate were 227.2±18.3, 135.2±11.0, and 104.4±5.3, respectively. Immediately post-biofeedback, these values changed to 213.7±15.2, 126.9±8.5, and 99.2±3.6. However, sustained long-term blood pressure reduction was not observed. Conclusions: The findings suggest that biofeedback therapy induces a short-term reduction in blood pressure in cases of malignant hypertension, potentially associated with autonomic nervous system regulation. Integrating biofeedback with other Korean medicine treatments, such as acupuncture or moxibustion, may offer a comprehensive approach for managing malignant hypertension.