Objectives: To evaluate the therapeutic potential of Gymnema sylvestre (GS) leaf ethanolic extract against letrozole induced polycystic ovarian syndrome (PCOS) in rats. Methods: Thirty female virgin rats (180-250g) with regular estrus cycles were used and divided into five groups of six animals each. Group-I serves as normal control receives 1ml of 0.5% carboxyl methyl cellulose orally; group-II to V were treated with letrozole (1mg/kg/b.w. p.o.) for 21 days to induce PCOS. Induction of PCOS was confirmed by measuring menstrual irregularity. After induction of PCOS, group-II serves as PCOS control, group-III receives metformin (20 mg/kg/b.w. p.o.) as standard, and group-IV to V treated with G. sylvestre ethanolic extract 200mg/kg/b.w. and 400mg/kg/b.w. p.o. respectively for 28 days. After completion of the treatment schedule oral glucose tolerance test was carried out, followed by serum lipid profile (LDL, VLDL, HDL, and TG), and hormonal analysis was carried out. Then the animals have sacrificed and the ovaries were then processed for histological examination. Results: The results of this study exhibited irregularity in the estrus cycle, a significant increase in serum blood glucose, and an altered serum lipid profile in PCOS control. In addition, the PCOS control rats showed a significant increase in serum luteinizing hormone, testosterone, and a decrease in estrogen, follicle-stimulating hormone, and progesterone. These changes were significantly reversed by G. sylvestre in a dose dependent manner. Histopathology of the ovary also showed an almost normal ovary in the treatment groups. Conclusion: In conclusion, the treatment of ethanolic leaf extract of Gymnema sylvestre reduces insulin resistance by improving glucose utilization, regularize menstrual irregularity and promote ovulation by correcting the hormonal irregularities and improve the development of follicles in PCOS condition. © 2023 Elsevier B.V., All rights reserved.