Polycystic ovary syndrome (PCOS) is the most frequent endocrinopathy in reproductive-aged women, mainly characterized by oligoanovulation and hyperandrogenism. Insulin resistance represents a major pathophysiological feature of the syndrome and, therefore, insulin-sensitizing agents (metformin and thiazolidinediones) have been applied in PCOS women. However, the clinical use of insulin sensitizers in PCOS has been debated. The aim of the current review was to update the knowledge regarding the role of metformin and thiazolidinediones in PCOS treatment, focusing on recently published studies. Several clinical trials examined metformin effectiveness on lipids, atherosclerosis and inflammatory markers, hormone levels, menstrual irregularities, ovulation induction, fertility, hirsutism, obesity parameters and quality of life in PCOS women. Metformin treatment was shown to improve these features, although conflicting results were also reported. Only one study investigated pioglitazone effect on PCOS, reporting an improved IVF outcome in clomiphene citrate-resistant PCOS patients. Finally, both metformin and pioglitazone, as a part of a low-dose polytherapy, exerted beneficial effects on lipids, androgen levels, hirsutism and markers of atherosclerosis in nonobese PCOS women. Further research, including larger randomized controlled trials and meta-analyses, is needed to clarify the role of metformin and thiazolidinediones in the treatment of clinical and biochemical PCOS characteristics.