Objectives: The aim of this study was to evaluate the impact of acupuncture on hot flashes in breast cancer patients taking tamoxifen as an adjuvant antiestrogen therapy in Korea. Design: This trial was a randomized, no-treatment-controlled, single-blind, multi-center trial. Participants were randomized 1:1 into the acupuncture group or into the no-treatment control group. Location: This trial was conducted at Daegu Catholic University Hospital and Daegu Haany University Korean Medicine Hospital in Daegu, Republic of Korea. Participants: Patients with moderate to severe symptoms of hot flashes while receiving adjuvant antiestrogen therapy using tamoxifen after surgery for breast cancer were included. Interventions: In the acupuncture group, acupuncture was performed three times a week for 4 consecutive weeks at five predetermined points. The control group received no treatment during the study period. Study Outcome Measures: As a primary outcome, the severity of hot flashes was measured on the visual analogue scale (VAS) and total hot flash score. In addition, the quality of life (QoL) of participants was assessed as a secondary outcome. Results: A total of 30 patients were included in this study, 15 each in the acupuncture group and the control group. The participants in the acupuncture group significantly decreased the severity of hot flashes evaluated with both VAS and total hot flash scores compared with participants in the control group. Also, the acupuncture group showed improved score of a global health status/QoL scale and functional scales assessed with the European Organisation for Research and Treatment of Cancer QoL questionnaire-core questionnaire, compared with those in the control group. This trend was maintained 4 weeks after acupuncture treatment. No adverse events have been reported in this study. Conclusions: Acupuncture was effective and safe in improving hot flashes in Korean breast cancer patients receiving adjuvant antiestrogen therapy with tamoxifen, and it improved the QoL. Clinical Trial Registration: KCT0007829.