Emergency physicians are expected to diagnose the health conditions of strangers presenting with every imaginable symptom within the narrowest time frames in an often chaotic, disruptive, and overcrowded work environment. It shouldn’t be surprising that diagnostic errors are a leading cause of emergency department malpractice lawsuits. In this Claims Rx, we present an emergency department delayed diagnosis of sepsis case based on a closed medical liability claim. Systems issues and defendant physician diagnostic reasoning are analyzed. Based on that analysis, risk reduction and patient safety strategies for administrators and clinicians are introduced to address diagnostic error in the ED from multiple angles.