Background: Hospital-affiliated freestanding emergency departments (FREDs) are rapidly proliferating in some states and have been the subject of recent policy debate. As FREDs' role in acute care delivery is expanding in certain regions, little is known about the quality of care that they provide for their sickest patients. Our aim was to compare timeliness of emergent care at FREDs and hospital-based EDs (HEDs) for patient visits with selected high-acuity and time-sensitive conditions. Methods: We performed a retrospective observational analysis of adult patient visit data from 19 FREDs and five HEDs from one health system over a 1-year period. Median times to events and hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated via Cox regression. Results: The median time to electrocardiogram for visits with chest pain was 10 minutes at FREDs and 9 minutes at HEDs (HR = 0.91 [CI = 0.87 to 0.96]). Time to cardiac catheterization lab for visits with ST-segment elevation myocardial infarction (STEMI) was 78 minutes at FREDs, inclusive of transfer time, and 31 minutes at HEDs (HR = 0.41 [CI = 0.24 to 0.71]). Time to computed tomography for visits with stroke was 37 minutes at FREDs and 29 minutes at HEDs (HR = 0.42 [CI = 0.31 to 0.58]). Among visits with sepsis, FREDs had longer times to lactate collection (HR = 0.41 [CI = 0.30 to 0.56]), blood culture collection (HR = 0.24 [CI = 0.11 to 0.51]), and antibiotic administration (HR = 0.61 [CI = 0.26 to 1.42]). Beta agonists were administered for visits with asthma exacerbations in 24 minutes at FREDs and 44 minutes at HEDs (HR = 2.50 [CI = 2.34 to 2.68]), with similar times for anticholinergic and corticosteroid administration. Conclusions: Freestanding EDs provided more timely care than HEDs for visits with asthma exacerbation and less timely care for acute chest pain, stroke, and sepsis, although absolute differences were small. Even though STEMI patients at FREDs required transfer for catheterization, they tended to receive care in line with national guidelines.