Aim: The aim of this study is to investigate the correlation between Body Mass Index (BMI) and sputum conversion rates in patients with sputum-positive pulmonary tuberculosis. Materials and Methods: A total of 100 patients, diagnosed with sputum-positive pulmonary tuberculosis, were enrolled in the study. The inclusion criteria consisted of patients aged 18 years and older, who were sputum-positive for acid-fast bacilli (AFB) at the start of treatment and initiated on the standard ATT regimen. At baseline, detailed demographic data including age, gender, and residence were recorded. BMI was calculated by measuring the weight (in kilograms) and height (in meters) of each patient at the time of diagnosis and after 3 months of ATT, after 6 month of ATT and After end of the treatment. Sputum samples were collected at baseline and at the end of 3, months, 6 months and end of treatment to assess sputum conversion. Results: Underweight patients had the lowest sputum conversion rate at 66.7% (p=0.032), indicating a statistically significant delay in conversion compared to patients in other BMI categories. Normal weight patients had the highest conversion rate (87.5%), followed by overweight patients (75%) and obese patients (100%). The significance in the underweight category underscores the impact of poor nutritional status on treatment efficacy. By this point, conversion rates were high across all BMI categories, with 93.3% of underweight patients, 97.5% of normal weight patients, 95% of overweight patients, and 90% of obese patients achieving sputum-negative status. The p-value for underweight patients (p=0.043) remains statistically significant, emphasizing the challenge faced by underweight patients in achieving full recovery even after a year of treatment. Conclusion: The study demonstrated a clear correlation between BMI and sputum conversion rates in pulmonary tuberculosis patients undergoing anti-tubercular treatment. At 3 months, underweight patients showed significantly slower sputum conversion (40%) compared to other BMI groups, indicating early challenges in treatment. By 6 months, conversion rates improved across all groups, but underweight patients still lagged behind (66.7%). At the end of treatment, most patients achieved sputum-negative status, though underweight patients continued to experience a slight delay (93.3%). These findings underscore the critical role of nutritional status in enhancing TB treatment outcomes.