Background: - Weight gain is gaining of fat and lean body which is lost from the diseases. It is defined as an increment of weight by≥5% from baseline after intensive phase. Ethiopia remains one of the highest tuberculosis burden countries in the world and tuberculosis is one of the most imperative health problems in the country. Patients with tuberculosis often suffer from severe weight loss and are used as useful marker to predict TB treatment outcome. Since TB is the single leading infectious cause of mortality in the country and weight of TB patient is associated with TB treatment outcome. Objective: - To assess weight gain and associated factors among adults of tuberculosis patients in Bahir Dar public health facilities, North West Ethiopia. Methods: - A facility based cross-sectional study was conducted from August 28-Decemeber 28 /2019 among all tuberculosis patients with the age of 18 and above who were under follow up in Tuberculosis Unit of Bahir Dar public health facilities. Systematic random sampling technique with proportional allocation was used for public health facilities in Bahir Dar. Weight of patients was recorded from TB treatment units at the time of diagnosis during the 2 months of intensive phase treatment. A total of 391 TB patients were enrolled. Data were entered in Epi-Info version 7 and exported to SPSS version 23 for analysis. A level of significance P< 0.25 was taken as cutoff point to identify candidate variables for multivariable binary logistic regression and level of significance 0.05 was taken for significance association for multiple binary logistic regression analysis. Results: - The finding of this study shows that 277 (70.8%) with 95% CI (66.5, 75.4) of TB patients had weight gain during intensive phase of TB treatment. Supplementary feeding; AOR [4.548, 95% CI (2.36, 8.75)], HIV infection AOR; [3.22, 95% CI (1.82, 5.67 )]. , parasitic infection AOR [4.41; 95%CI: (2.30, 8.43)] diabetics patients; AOR [5.68, 95% CI (2.09, 15.41)], and adherence of TB treatment AOR [3.50, 95% CI (1.542, 7.95)] were factors significantly associated with weight gain during intensive phase. Conclusion: -The magnitude of weight gain in this study was found to be 70.8%. Supplementary feeding, co-morbidity and adherence of patients during the course of TB treatment in intensive phase were associated factors of weight gain. Key words: - tuberculosis, weight gain, treatment out come