Objectives: Prolonged emergency department to ICU waiting time may delay intensive care treatment, which could negatively affect patient outcomes. The aim of this study was to investigate whether emergency department to ICU time is associated with hospital mortality. Design, Setting, and Patients: We conducted a retrospective observational cohort study using data from the Dutch quality registry National Intensive Care Evaluation. Adult patients admitted to the ICU directly from the emergency department in six university hospitals, between 2009 and 2016, were included. Using a logistic regression model, we investigated the crude and adjusted (for disease severity; Acute Physiology and Chronic Health Evaluation IV probability) odds ratios of emergency department to ICU time on mortality. In addition, we assessed whether the Acute Physiology and Chronic Health Evaluation IV probability modified the effect of emergency department to ICU time on mortality. Secondary outcomes were ICU, 30-day, and 90-day mortality. Interventions: None. Measurements and Main Results: A total of 14,788 patients were included. The median emergency department to ICU time was 2.0 hours (interquartile range, 1.3–3.3 hr). Emergency department to ICU time was correlated to adjusted hospital mortality ( p < 0.002), in particular in patients with the highest Acute Physiology and Chronic Health Evaluation IV probability and long emergency department to ICU time quintiles: odds ratio, 1.29; 95% CI, 1.02–1.64 (2.4–3.7 hr) and odds ratio, 1.54; 95% CI, 1.11–2.14 (> 3.7 hr), both compared with the reference category (< 1.2 hr). For 30-day and 90-day mortality, we found similar results. However, emergency department to ICU time was not correlated to adjusted ICU mortality ( p = 0.20). Conclusions: Prolonged emergency department to ICU time (> 2.4 hr) is associated with increased hospital mortality after ICU admission, mainly driven by patients who had a higher Acute Physiology and Chronic Health Evaluation IV probability. We hereby ...