Aim: To evaluate the association between Body Mass Index (BMI) and the severity of Chronic Obstructive Pulmonary Disease (COPD) in patients classified into severity groups A, B and E as per the GOLD (Global Initiative for Chronic Obstructive Lung Disease) classification. Material and Methods: A cross-sectional observational study was conducted to evaluate the association between Body Mass Index (BMI) and the severity of Chronic Obstructive Pulmonary Disease (COPD) in patients classified into severity groups A, B, and E, as per the GOLD (Global Initiative for Chronic Obstructive Lung Disease) classification. The study was carried out in the pulmonary medicine department of a tertiary care hospital over a period of 12months and a total of 90 patients were taken. Results: Underweight patients were more frequently found in Group B (n=6) and Group E (n=4), while normal-weight patients had a higher prevalence in Group A (n=15) and Group B (n=20). Overweight patients were evenly distributed across the severity groups, while obese patients were most common in Group E (n=5). The p-value for underweight patients (p=0.036) shows a statistically significant association with COPD severity, suggesting that underweight patients tend to have more severe COPD (Group E). For the other BMI categories, the p-values indicate that the association was not statistically significant, though there was a trend toward higher BMI being associated with increased severity (Group E). Conclusion: We concluded that a statistically significant association between BMI and COPD severity for the underweight category, suggesting that underweight individuals may have a higher prevalence of more severe COPD. Although no statistically significant differences were found for other BMI categories (normal weight, overweight, and obese). This highlights the importance of considering BMI in managing COPD severity, particularly for underweight patients.