Primary infertility affects a significant proportion of couples and is often attributed to female factors. Obesity, which is associated with increased levels of the hormone leptin, is a known risk factor for female infertility. This cross-sectional study aimed to investigate the association between BMI and leptin levels in primary infertile females at Al-Nuaman Hospital and Al-Salama private hospital from September 2022 to March 2023. A total of 100 females were enrolled, and their BMI and serum leptin levels were measured. The participants were divided into four groups: Group 1 (normal weight, fertile), Group 2 (overweight infertile), Group 3 (obese infertile), and Group 4 (severely obese infertile) women, each consisting of 25 participants, categorized based on their BMI: normal BMI (18.5–24.9 kg/m²), overweight BMI (25–29.9 kg/m²), obesity BMI (≥30 kg/m²), and severely obese BMI (35-40 kg/m²). The mean leptin levels were compared between the four groups using ANOVA, and the association between BMI and leptin levels was assessed using Pearson's correlation coefficient. The study revealed a highly significant correlation between primary infertility and the parameters (BMI and leptin) (P < 0.001) and showed a positive correlation between leptin and BMI. It was shown that primary infertile females with a high BMI have elevated serum leptin levels. This underscores the importance of weight management in addressing primary female infertility.