Evaluating the outcomes of tuberculosis treatment and understanding the specific reasons for unfavorable treatment outcome are important in evaluating the effectiveness of tuberculosis control program. A retrospective study was conducted to assess tuberculosis treatment outcomes and associated factors among smear positive pulmonary tuberculosis patients in zone-one health facilities of Afar regional state, Ethiopia. A total of 380 smear positive pulmonary tuberculosis patients' registration book recorded with complete information from Jan 2011 to Dec 2013 were analyzed. Of 380 patients included in the analysis, 238 were male and 142 female with mean age of 30.7. Overall treatment outcome were 128 (33.7%) cured, 192 (50.2%) completed, 17 (4.5%) died, 1 (0.3%) treatment failure, 34 (8.9%) default and 8 (2.1%) transfer out. Treatment success rate was 81.8%. There was statistically significance association between age (p-value=0.000), sex (p-value=0.018), HIV status (p-value=0.000), four week attendance (p-value=0.000), sputum follow up test (p-value=0.000), and treatment outcome year (p-value=0.000), and treatment success (p-value=0.000). Treatment success rate almost reached to the WHO targets although yet need to work a lot for fulfillment of global targets. Regular four week attendance in continuation phase and doing follow up sputum test with unsuccessful outcome for smear positive tuberculosis patient were vital.