Polycystic ovary syndrome (PCOS) is a disorder characterized by insulin resistance, low-grade inflammation, and increased adipose tissue. The very low-carbohydrate ketogenic diet (VLCKD) has been suggested to reduce obesity risks in PCOS. This study aimed to update the evidence on effects of the very low-carbohydrate ketogenic diet in women with PCOS. Searches were conducted in electronic databases for randomized clinical trials (RCTs) addressing the research question. The values for the meta-analysis were presented as weighted mean difference (WMD). Twelve studies were included in the qualitative analysis and eleven in the quantitative analysis. Significant reductions were observed in anthropometric outcomes: weight [WMD: -9.57 kg; p < 0.0001], waist circumference [WMD: -7.75 cm; p < 0.0009], fat body mass [WMD: -7.44 kg; p = 0.0008], body mass index [WMD: -3.45 kg/m2; p < 0.0001] and waist-to-hip ratio [WMD: -0.02; p < 0.0034]. Hormonal improvements included free testosterone [WMD: -0.31 ng/dL; p < 0.0001], total testosterone [WMD: -7.21 ng/dL; p<0.0001], sex hormone binding globulin [WMD: 15.22 nmol/L; p =0.0035], luteinizing hormone (LH) [WMD: -3.97 U/L; p =0.0008], and LH/FSH ratio [WMD: -1.04; p =0.0053], but not for follicle-stimulating hormone (FSH) levels [WMD: 1.23 mUI/mL; p =0.12]. Significant changes in metabolic markers were seen in blood glucose [WMD: -9.65 mg/dL; p =0.0031], insulin [WMD: -2.41 mg/dL; p =0.0387], homeostatic model assessment for insulin resistance [WMD: -2.46; p =0.0123], and triglycerides [WMD: -29.95 mg/dL; p =0.0188]. VLCKD shows significant benefits in managing body composition, reducing hyperandrogenism, balancing sex hormones, and improving glucose metabolism in PCOS.