Background and Objectives: Polycystic ovary syndrome (PCOS) is a frequent multifactorial endocrinopathy affecting women in the reproductive period, often associated with infertility and metabolic disorders. The use of animal models helps to better understand etiopathogenesis, enabling the examination of the effects of certain drugs in order to discover the best possible therapeutic approach. We tried to investigate the additional effect of estradiol-valerate (EV) and high-fat diet (HFD) in female rats to explore PCOS-related alterations with special focus on oxidative stress. Materials and Methods: Animals were divided into three groups: control group (CTRL, n = 6), estradiol-valerate group (EV, n = 6), and estradiol-valerate group on HFD (EV + HFD, n = 6). PCOS was induced by single subcutaneous injection of long-acting EV in a dose of 4 mg/per rat. We tried to improve the metabolic characteristics of the PCOS animal model by adding HFD, so the CTRL and EV group had a regular diet, while the EV + HFD group had HFD during the induction period of 60 days. Results: We observed alterations of anthropometric parameters and hormonal disturbances, along with estrus cycle impairment reassembly to obese-type PCOS phenotype. Moreover, glucose metabolism was impaired after addition of HFD to EV protocol, contrary to EV administered alone. Histological analysis confirmed more numerous cystic follicles after the combination of EV and HFD protocol. The alterations of oxidative stress markers could be related to and serve as the mechanistic base for development of PCOS-related endocrine, reproductive, and metabolic properties. Conclusions: The additive effect of EV and HFD was obvious in the majority of the parameters observed. Our study strongly demonstrated metabolic as well as reproductive properties of PCOS in rats.