Recognising and responding to clinical deterioration is a safety priority. The aim of this study was to determine the frequency, nature, and response of emergency department Nursing Shift Leaders to episodes of escalation of care for patient clinical deterioration.A prospective exploratory descriptive design was used. Participants were recruited from the senior nurses at the study site that fulfilled the role of being in charge of the ED. Study data were collected between 29 October and 17 December 2015 across various shifts using an observation tool developed specifically for this study.This study had three major findings. First, escalation of care for clinically deteriorating patients to the Nursing Shift Leader occurs frequently. There were 37 observed escalations of care, equating to 1.02 episodes per hour. Second, Nursing Shift Leaders rely on clinical emergency nursing skills to recognise, prioritise and respond to escalation of care for clinically deteriorating patients. Finally, the Nursing Shift Leaders’ role in responding to escalation of care for clinical deterioration is multifaceted.The Nursing Shift Leaders’ role in responding to escalation of care for clinical deterioration is complex and includes navigation of a multifaceted team environment and logistical challenges unique to the time pressured, unpredictable ED milieu.