OBJECTIVE: Endoleaks may be seen at case completion of endovascular abdominal aortic aneurysm repair (EVAR), and the presence of an endoleak may impact outcomes. However, the clinical implications of various endoleaks seen during follow-up is not well-described. Therefore, we studied the impact of endoleaks at completion and at follow-up on mid-term outcomes. METHODS: We reviewed patients who underwent EVAR from 2003 to 2016 within the Vascular Quality Initiative-Medicare database and identified patients with endoleak at procedure completion and during follow-up, excluding those presenting with rupture. We stratified cohorts by presence of completion and follow-up endoleak subtypes. The primary outcome was 5-year survival, and secondary outcomes included 5-year freedom from reintervention and freedom from rupture. We used Kaplan-Meier estimates and log-rank tests to analyze differences in time-to-event endpoints. RESULTS: Of 21,745 patients with completion endoleak data, 5085 (23%) had an endoleak. Compared with those without endoleak, those with type I endoleaks had lower 5-year survival (69% vs 75%; P < .001), type II endoleaks had higher survival (79%; P < .001), and types III, IV, and indeterminate were not statistically different (73%, 73%, and 75%, respectively). Freedom from reintervention for types I and III endoleaks were significantly lower than no endoleak cohort (I: 76%; P < .001; III: 72%; P < .001 vs 83%), but freedom from rupture was higher for those with type II and III endoleak (95% and 97% vs 94%; P < .001). Of 14,479 patients with detailed follow-up endoleak data, 2290 (16%) had an endoleak. Compared with those without endoleak, types I and III had significantly lower 5-year survival (I: 80%; P = .002; III: 66%; P < .001 vs 84%), but there were no differences for types II (82%) and indeterminate (77%). Those with any type of follow-up endoleak had lower 5-year freedom from reintervention (I: 70%; P < .001; II: 76%; P = .006; III: 36%; P < .001; indeterminate: 60%; P = .007 vs 84%), and lower freedom from rupture (I: 92%; P < .001; II: 91%; P = .16; III: 88%; P = .01; indeterminate: 90%; P = .11 vs 94%). CONCLUSIONS: Compared with patients with no endoleak, those with type I completion endoleaks have lower 5-year survival and freedom from reintervention. Patients with types I and III follow-up endoleaks also have lower survival, and any endoleak at follow-up is associated with lower freedom from reintervention and freedom from rupture. These data highlight the importance of careful patient selection and close postoperative follow-up after EVAR, as the presence of endoleaks, specifically type I and III, over time portends worse outcomes.