The aim of this study was to describe the cause of the recent improvement in the outcomes of patients who experienced in-hospital cardiac arrest. We retrospectively analyzed the in-hospital arrest registry of a tertiary care university hospital in Korea between 2005 and 2009. Major changes to the in-hospital resuscitation policies occurred during the study period, which included the requirement of extensive education of basic life support and advanced cardiac life support, the reformation of cardiopulmonary resuscitation (CPR) team with trained physicians, and the activation of a medical emergency team. A total of 958 patients with in-hospital cardiac arrest were enrolled. A significant annual trend in in-hospital survival improvement (odds ratio = 0.77, 95% confidence interval 0.65-0.90) was observed in a multivariate model. The adjusted trend analysis of the return of spontaneous circulation, six-month survival, and survival with minimal neurologic impairment upon discharge and six-months afterward revealed similar results to the original analysis. These trends in outcome improvement throughout the study were apparent in non-ICU (Intensive Care Unit) areas. We report that the in-hospital survival of cardiac arrest patients gradually improved. Multidisciplinary hospital-based efforts that reinforce the Chain of Survival concept may have contributed to this improvement.