The objective of this study was to investigate the association between shift level nurse staffing, and survival to discharge for patients sustaining an in-hospital cardiac arrest (IHCA). In many instances, the most likely first responder to witness IHCA and provide needed treatment is the registered nurse. Delays in treatment are associated with decreased survival; every minute is important during cardiac arrest. Little if any comprehensive research has been undertaken to determine the features of nursing that are important in the outcomes of cardiac arrest, however. Thus, there is a critical need to thoroughly examine if and how nursing affects survival patients experiencing in-hospital cardiac arrest. This study was a cross sectional secondary analysis of an in-hospital cardiac arrest registry and staffing data obtained from hospital productivity reports. Registered nurse hours per patient day were analyzed during the nursing shift that the cardiac arrest occurred. Generalized estimating equation models were used account for the clustering of patients within units. The sample consisted of adult patients aged 18 and older who sustained an in hospital cardiac arrest between May 2004 and December 2009 in one Mid-western academic hospital. The final analytic sample consisted of 299 patients in 22 medical surgical, rehabilitation and intensive care units. One additional hour per patient day of RN care results in 19% greater odds of surviving to discharge while controlling for patient and unit characteristics in the model. Shift- level staffing measured at the time of the event was found to positively predict in-hospital cardiac arrest survival. The findings from this study will serve to inform nursing practice with regard to the importance of staffing levels which can impact survival. Response times to cardiac arrests depend on recognizing the arrest and the ability to respond and provide treatment in a timely manner. This is directly the result of the availability of staff to react to such a situation. Moreover, a closer perspective in examination of a specific event and shift-level staffing, the more likely important process improvement initiatives will be appropriate and successful.