Aim: The objective of the present study was to assess the effect of moderate intensity exercises on P-300 component of event related potential during different menstrual phases in young obese and non-obese women of Bihar. Methods: It was a cross-sectional observational study conducted at Patna Medical College, Patna, Bihar, India, on young normally menstruating women with normal auditory capability of age group 18–35 years, BMI (Normal =18-24.9 kg/m2 and Obese>25 kg/m2 ) according to the WHO criteria and without any major chronic illness and neurocognitive deficit. The ethical approval for this study was obtained from Institutional Ethical Committee. Results: It is evident from the study that the participants were mostly in the age group of 19– 21 years. BMI of the normal subjects was mostly in between 19.4 and 22.13. BMI of the obese subjects was mostly in between 25.4 and 30.13. Waist–hip ratio (WHR) of the subjects was mostly little above normal range (normal being <0.8). Observation showed that most of the subjects perceived physical activity as light to extremely light except for a few subjects. The amplitude and latencies of P300 ERP in obese and non-obese showed no significant difference at resting state (pre-exercise) during early follicular and mid-luteal phases. The amplitude of P300 ERP displayed no significant change in post-exercise session in comparison to pre-exercise session in both phases among obese and non-obese subjects. However, P300 latency showed significant decrease in post-exercise session when recorded at Cz (P = 0.024, P = 0.05) as well as Pz position (P = 0.03, P = 0.003) in both phases of menstrual cycle among both groups. However, P300 latency recorded at Fz position displayed no significant change in post-exercise session in comparison to pre-exercise session in nonobese and obese persons during both phases of menstrual cycle. Conclusion:- The inference from present study showed that moderate intensity exercises caused significant decline in latency of P300 ERP in the subjects (both non-obese and obese) during both follicular and luteal phases of menstrual cycle. Therefore, it indicates that even moderate intensity exercise significantly improves allocation of attentional resources and working memory in the subjects. Hence, it enhances cognitive functioning of the both nonobese and obese individuals but to a lesser extent among obese subjects.