Background. Tuberculosis remains a major global health problem. It causes ill-health among millions of people each year and ranks alongside the human immunodeficiency virus (HIV) as a leading cause of death worldwide. Purpose. To assess the outcome of tuberculosis treatment and to identify factors associated with tuberculosis treatment outcome. Methods. A five-year retrospective cross-sectional study was employed and data were collected through medical record review. Data were analyzed using SPSS version 16 and binary and multiple logistic regression methods were used. A value of less than 0.05 was considered as statistically significant in the final model. Results. Out of the 1584 pulmonary TB patients (882 males and 702 females) including all age group, 60.1% had successful outcome and 39.9% had unsuccessful outcome. In the final multivariate logistic model, the odds of unsuccessful treatment outcome was higher among patients of weight category 30-39.9 kg (AOR = 1.51, 95% CI: 1.102-2.065) and smear negative pulmonary TB (AOR = 3.204, 95% CI: 2.277-4.509) and extrapulmonary TB (AOR = 3.175, 95% CI: 2.201-4.581) and retreatment (AOR = 6.733, 95% CI: 3.235-14.013) and HIV positive TB patients (AOR = 1.988, 95% CI: 1.393-2.838) and unknown HIV status TB patients (AOR = 1.506, 95% CI: 1.166-1.945) as compared to their respective comparison groups. Conclusion. In this study, high proportion of unsuccessful treatment outcome was documented. Therefore emphasis has to be given for patients with high risk of unsuccessful TB treatment outcome and targeted interventions should be carried out.