Polycystic ovary syndrome (PCOS) is an endocrine disease associated with infertility and metabolic disorders in reproductive-aged women. In this study, we evaluated the expression of eight genes related to endometrial function and their DNA methylation levels in the endometrium of PCOS patients and women without the disease (control group). In addition, eight of the PCOS patients underwent intervention with metformin (1500 mg/day) and a carbohydrate-controlled diet (type and quantity) for three months. Clinical and metabolic parameters were determined, and RT-qPCR and MeDIP-qPCR were used to evaluate gene expression and DNA methylation levels, respectively. Decreased expression levels of , , and genes and increased DNA methylation levels of the promoter were found in the endometrium of PCOS patients compared to controls. After metformin and nutritional intervention, some metabolic and clinical variables improved in PCOS patients. This intervention was associated with increased expression of , , and genes and reduced DNA methylation levels of the promoter in the endometrium of PCOS women. Our preliminary findings suggest that metformin and a carbohydrate-controlled diet improve endometrial function in PCOS patients, partly by modulating DNA methylation of the gene promoter and the expression of genes implicated in endometrial receptivity and insulin signaling.