The optimal duration of dual antiplatelet therapy (DAPT) after treatment of chronic total occlusions (CTO) with percutaneous coronary intervention (PCI) is unknown. We aimed to determine if extended (> 12 months) DAPT was associated with a net clinical benefit. The study population included patients who underwent successful CTO PCI within Kaiser Permanente Northern California between 2009 and 2016. Baseline demographic, clinical, and procedural characteristics were compared for patients on DAPT ≤ versus > 12 months. Clinical outcomes (death, myocardial infarction (MI), and ≥ Academic Research Consortium type 3a bleeding) were compared beginning 12 months after PCI using Cox proportional hazards models. We also adjudicated individual causes of death. 1,069 patients were followed for a median of 3.6 years (Interquartile Range = 2.2 to 5.5) following CTO PCI. Patients on DAPT ≤ 12 months (n = 597, 56%) were more likely to have anemia, end stage renal disease, and previous MI. After adjustment for between group differences, > 12 months of DAPT was associated with lower death or MI (hazard ratio [HR]: 0.66; 95% confidence interval [CI]: 0.47 to 0.93) and lower death (HR: 0.54; 95% CI: 0.36 to 0.82). There were no associations with MI (HR: 0.91; 95% CI: 0.55 to 1.5) or bleeding (HR 1.1; 95% CI: 0.50 to 2.4), but a numerically higher proportion of patients on shorter v. longer DAPT died of a cardiovascular cause (37% vs 20%, p = 0.10). In conclusion, > 12 months of DAPT was associated with lower death or MI, without an increase in bleeding. Prospective studies are needed to evaluate the optimal duration of DAPT in this unique subgroup.