Premenopause is characterized by fluctuations in estrogen levels, which can affect ovarian follicle development and overall reproductive health. This study aimed to evaluate the impact of Ocimum basilicum (basil) leaf extract on ovarian follicles and serum estrogen concentrations in premenopausal Wistar rats. Twenty-four female rats were divided into four groups: a control group receiving distilled water and three experimental groups administered basil leaf extract at doses of 100, 200, and 400 mg/kg body weight, respectively, for 28 days. Histological examination of the ovaries was conducted to assess follicular development, and serum estrogen levels were measured using ELISA. Results demonstrated a dose-dependent increase in the number of healthy ovarian follicles and a significant elevation in serum estrogen concentrations in the treatment groups compared to the control (p < 0.05). These findings suggest that Ocimum basilicum leaf extract may enhance ovarian function and estrogen production, indicating its potential as a natural alternative for supporting reproductive health during premenopause.