Objective : To observe the effectiveness of Jayeumganghwa-tang on hot flush of a breast cancer patient who takes tamoxifen. Methods : For six weeks a dosage witch contained 13.92g of Jayeumganghwa-tang was administered 3 times (30 mins after meal) per day, for improvement of hot flush. No other therapies like hormone therapy or substituted therapy were done. Results : As a result of 6 weeks of Jayeumganghwa-tang therapy, the patient who suffered hot flush on taking tamoxifen showed improvement on several indices, including frequency, intensity and point of hot flush, Beck Depression Inventory-K (BDI-K) which shows uneasiness and sadness, and also Functional Assessment Cancer Therapy - Breast (FACT-B) which is an index of life quality of breast cancer patients. But no changes on female hormones like follicle-stimulating hormone (FSH) or luteinizing hormone (LH) were observed. Conclusion : This case demonstrates 6 weeks of Jayeumganghwa-tang taking had no effect on female hormones but can reduce the hot flush by tamoxifen. This shows minimum evidence of safety and efficacy of Jayeumganghwa-tang on hot flush of breast cancer patient. However this is a single case study so further case-series research should be compiled.