Objectives: Successful treatment of pulmonary tuberculosis patients is the key to tuberculosis control. This study aimed to assess treatment outcomes of newly diagnosed sputum smear-positive pulmonary tuberculosis patients under directly observed treatment, short course (DOTS) in Anambra State, Nigeria and determine factors associated with unsuccessful treatment outcome. Methods:The prospective observational study was carried out at 3 TB/DOTS centres. A total of 213 newly diagnosed sputum smear-positive pulmonary tuberculosis patients were enrolled into the study. Diagnosis of pulmonary tuberculosis was based on Xpert MTB/RIF test and microscopy. Each patient was treated daily using a 6-month regimen recommended by WHO. For intensive phase, RHZE (150/75/400/275 mg) tablets were given for 2 months. RHZE contains the drugs rifampicin(R), isoniazid(H), pyrazinamide(Z) and ethambutol(E). For contamination phase, RH (150/75mg) tablets were given for 4 months. The patients were followed up till completion of treatment and treatment outcomes recorded as per WHO guidelines. Results:Out of 213 patients, 181(85%) were cured, treatment completed in 3(1.4%) patients. Overall, treatment success rate was 86.4%. Exactly 24 (11.3%) patients were lost to follow up, treatment failed in 4(1.9%) and 1(0.5%) patient died. Treatment success rate decreased with aging as younger patients (15-24 years old) showed better treatment outcomes (90%) than older patients (> 65 years) at 71.4%. Unsuccessful treatment outcomes were more prevalent among unemployed patients (18.8%), with no formal education (17.6%) and married ones (12.6%). Conclusion:Treatment success rate in Anambra State was 86.4%. Lost to follow up (default rate) was high (11.3%). Aging, occupation and level of education were associated with unsuccessful treatment outcomes. It is therefore important to reduce default in treatment through proper counseling of pulmonary tuberculosis patients at TB/DOTS centres.