Background: Hot flashes are common menopausal vasomotor symptoms. Evidence for Achillea millefolium (yarrow) remains limited. This study compared the effects, direct intervention costs, and adverse-event profiles of yarrow extract and mindfulness-based cognitive therapy counseling versus routine care in postmenopausal women.

Methods: This three-arm, parallel-group randomized controlled trial was conducted from September 2021 to February 2022 in four Iranian health centers. Seventy-five eligible postmenopausal women were randomly assigned (1:1:1) to yarrow extract, MBCT counseling, or routine care (25/group). Yarrow participants received 500-mg A. millefolium capsules twice daily for 8 weeks; MBCT participants attended eight 120–150-minute sessions. The primary outcome was change in mean weekly hot-flash frequency; secondary outcomes were direct intervention costs and adverse events.

Results: All 75 randomized participants completed the 8-week intervention. Baseline mean weekly hot-flash frequency did not differ among groups (F = 0.450, p = 0.639), whereas a significant between-group difference was observed at week 8 (F = 30.487, p < 0.001). Mean weekly hot-flash frequency decreased by −3.58 (95% CI, −3.71 to −3.45) in the yarrow group and −3.55 (95% CI, −3.73 to −3.37) in the MBCT group, versus −0.69 (95% CI, −1.68 to 0.30) in controls. Both interventions differed from control (p < 0.001), but not from each other (p = 0.775). Mean costs were 345,320 and 836,000 Iranian Rials, respectively; mild gastrointestinal events occurred in 20% receiving yarrow.

Conclusion: Over 8 weeks, yarrow extract and MBCT counseling reduced mean weekly hot-flash frequency versus routine care. Yarrow had lower direct intervention costs but caused mild gastrointestinal adverse events. Larger placebo-controlled trials with longer follow-up and formal economic evaluations are needed.