Background Postoperative death is an important outcome after esophagectomy, and the Centers for Medicare & Medicaid Services currently uses 30-day mortality as a quality indicator for this operation. However, 30-day mortality may underestimate a patient's true postoperative death risk. The purpose of this study was to evaluate different mortality definitions using a large registry of patients undergoing esophagectomy for cancer. Methods Data were extracted from the Surveillance, Epidemiology and End Results-Medicare registry for patients with esophageal cancer who underwent esophagectomy between 2006 and 2009. Postoperative death was compared using four different definitions: 30-day, in-hospital, perioperative (in-hospital or 30-day), and 90-day mortality. Hierarchical logistic regression models evaluated the association between patient and tumor characteristics with survival at 30 and 90 days and the ability of death to differentiate between good hospitals and those that perform poorly. Results We identified 634 patients from 188 hospitals. The 90-day mortality rate (13.3%) was more than double the 30-day mortality rate (6.0%) in this patient population. Advanced age and diagnosis of chronic obstructive pulmonary disease were associated with an increased risk of 90-day mortality. Good or poor performers could not be determined using the 30-day or 90-day mortality rate. Conclusions There are clinically meaningful differences between postoperative mortality definitions after esophagectomy. Thirty-day mortality significantly underestimates a patient's true risk of death because this number more than doubles at 90 days in this elderly, Medicare population. Although neither 90-day nor 30-day mortality are adequate quality measures after esophagectomy, 90-day mortality is a better outcome measure because it provides a better understanding of true death risk for the surgeon and patient.