Emergency department (ED) overcrowding has been linked to an increased risk of adverse events in patients who are subsequently admitted to the hospital. Examining more than 14 million emergency department visits, this cohort study found that ED overcrowding, as measured by the average wait time for a patient to see a physician, was also associated with adverse events in patients who were discharged home from the ED. Specifically, increased wait times correlated with an increased risk of death and subsequent hospital admission in patients initially evaluated and discharged from the ED. This finding supports other studies that identify ED wait time as a potential patient safety risk, supporting efforts to reduce wait times and improve patient flow.