BACKGROUND: Hot flashes are a common side effect of endocrine therapy (ET) that contribute to poor quality of life and decreased treatment adherence. METHODS: Patients with breast cancer wo were receiving ET and experiencing hot flashes were enrolled through three parallel, randomized trials conducted in the United States, China, and South Korea. Participants were randomized to either immediate acupuncture (IA) or delayed acupuncture control (DAC). IA participants received 20 acupuncture sessions over 10 weeks, whereas DAC participants received usual care, then crossed over to acupuncture with a reduced intensity. The primary end point was a change in score on the endocrine symptom subscale of the Functional Assessment of Cancer Therapy (FACT)-Endocrine Symptoms between baseline and week 10. Secondary end points included the hot flash score and the FACT-Breast score. A planned pooled analysis of individual patient data was performed using longitudinal mixed models. RESULTS: In total, 158 women with stage 0-III breast cancer were randomized (United States, n = 78; China, n = 40; South Korea, n = 40). At week 10, IA participants reported statistically significant improvements in the endocrine symptom subscale score (mean change ± standard error: 5.1 ± 0.9 vs. 0.2 ± 1.0; p = .0003), the hot flash score (-5.3 ± 0.9 vs. -1.4 ± 0.9; p < .003), and the FACT-Breast total score (8.0 ± 1.6 vs. -0.01 ± 1.6; p = .0005) compared with DAC participants. The effect of the acupuncture intervention differed by site (p = .005). CONCLUSIONS: Acupuncture led to statistically and clinically meaningful improvements in hot flashes, endocrine symptoms, and breast cancer-specific quality of life in women undergoing ET for breast cancer in the United States, China, and South Korea.