Objective: High success rates for endoscopic dacryocystorhinostomy (END-DCR) in partial nasolacrimal duct obstruction (NLDO) have been reported, but comparisons with complete NLDO are lacking. This study compares the success of primary END-DCR with respect to the preoperative nasolacrimal duct patency and reviews factors associated with failure. Method: Retrospective review of END-DCRs performed at a tertiary referral center. Partial and complete NLDO were defined by the presence or absence of flow into the nose with lacrimal sac washout (SWO), respectively. Intraoperative findings including thickness of bone, level and state of the common canaliculus, state of inflammation, and contents of the lacrimal sac during END-DCR were recorded. For patients with at least 3 months follow-up, the outcome of resolution of epiphora (none/partial/complete), postop Jones 1 (J1; positive/ negative) and endoscopy of the neo-ostium (closed/partially or fully-open) were defined. Results: A total of 245 primary END-DCRs were reviewed (mean age, 63.6 ± 5.3 years, 70% women). Based on SWO, the groups were defined as 39.6% and 60.4% complete NLDO. Overall improvement in epiphora was 95.5%. In cases where symptoms improved, absence of flow into nose on SWO was associated with a higher rate of complete resolution (93.6% vs 84.9%, RR 1.102 [1.001, 1.213]). The ostia were fully open in 93.9% and postop J1 was positive in 97.1% of patients and were not different between groups. Conclusion: END-DCR is highly successful for both types of NLDO. Preoperative absence of flow into nose on SWO was associated with slightly higher chance of complete resolution.