This study investigated the efficacy of an open-label placebo (OLP) treatment for menopausal hot flushes. Women with at least five moderate or severe hot flushes per day were allocated to receive four weeks of OLP for twice a day or no-treatment. Intention-to-treat analyses included n = 100 women. In comparison to no-treatment, OLP reduced the log-transformed hot flush composite score (frequency × intensity) (mean difference in change: - 0.32, 95% CI [- 0.43; - 0.21], p < 0.001, Cohen's d = 0.86), hot flush frequency (- 1.12 [- 1.81; - 0.43], p = 0.02, Cohen's d = 0.51), and improved overall menopause-related quality of life (- 2.53 [- 4.17; - 0.89], p = 0.02, Cohen's d = 0.49). Twelve (24%) (vs. three [6%]) patients had 50% lesser hot flushes. Problem rating of hot flushes and subdomains of quality of life did not improve. After four weeks, the OLP group was further divided via randomization to continue or discontinue the treatment. Benefits were maintained at week 8 (log-transformed score: - 0.04 [- 0.06; 0.14], p = 0.45). There was no difference between taking placebos for 8 or 4 weeks (log-transformed score: 0.04 [- 0.17; 0.25], p = 0.73). Results indicate that open-label placebos may be an effective, safe alternative for menopausal hot flushes.