Polycystic ovary syndrome (PCOS) is a common, complex reproductive endocrinopathy characterized by menstrual irregularities, hyperandrogenism and polycystic ovaries. Lifestyle modification is a first‐line intervention; however, there are barriers to success for this form of self‐care, and women often seek adjunct therapies including herbal medicines. This pragmatic, randomized controlled trial, delivered in communities of Australia in overweight women with PCOS, compared the effectiveness and safety of a lifestyle intervention plus herbal medicine against lifestyle alone. All participants were helped to construct a personalized lifestyle plan. The herbal intervention consisted of two tablets. Tablet 1 contained Cinnamomum verum, Glycyrrhiza glabra, Hypericum perforatum and Paeonia lactiflora. Tablet 2 contained Tribulus terrestris. The primary outcome was oligomenorrhoea/amenorrhoea. Secondary outcomes were hormones; anthropometry; quality of life; depression, anxiety and stress; pregnancy; birth outcomes; and safety. One hundred and twenty‐two women gave their consent. At 3 months, women in the combination group recorded a reduction in oligomenorrhoea of 32.9% (95% confidence interval 23.3–42.6, p < 0.01) compared with controls, estimated as a large effect (ηp
2 = 0.11). Other significant improvements were found for body mass index (p < 0.01); insulin (p = 0.02) and luteinizing hormone (p = 0.04); blood pressure (p = 0.01); quality of life (p < 0.01); depression, anxiety and stress (p < 0.01); and pregnancy rates (p = 0.01). This trial provides evidence of improved effectiveness and safety for lifestyle intervention when combined with herbal medicines in women with PCOS. © 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd