<p>Polycystic ovary syndrome (PCOS) is a common endocrine disorder in reproductive-aged women, frequently associated with insulin resistance (IR) and metabolic syndrome (MetS). Given the limitations of conventional therapies, complementary interventions targeting metabolic pathways are needed. This randomized clinical trial investigated the adjunctive effects of apple cider vinegar (ACV) on MetS components and IR in PCOS patients receiving standard metformin treatment (1500&#xa0;mg/day). In this 12-week randomized controlled trial, 94 women meeting the Rotterdam criteria for PCOS, NCEP ATP III criteria for MetS, and HOMA-IR &gt; 2.5, were randomized 1:1 to receive either ACV capsules (1500&#xa0;mg/day) or placebo. Primary outcomes were changes in IR and MetS components; secondary outcomes included serum testosterone, hirsutism (modified Ferriman–Gallwey score), sexual function (FSFI), and quality of life (mPCOSQ). The results showed resolution of MetS was significantly higher in the ACV group (74.5%) than controls (40.4%) (<i>p</i> = 0.001). Significant reductions in IR (<i>p</i> = 0.01), hirsutism (<i>p</i> = 0.003), and improvements in sexual function (<i>p</i> &lt; 0.001) and quality of life (<i>p</i> = 0.001) were observed in the intervention group. These results demonstrate that ACV supplementation may offer a beneficial adjunctive strategy for improving metabolic and quality-of-life parameters in women with MetS, IR, and PCOS.</p><p>Trial registration: IRCT20150905023897N7, registered on 11/12/2023.</p>