Purpose: Studies have reported controversial results regarding the effect of rapid response teams (RRTs) on decreasing in-hospital mortality. Therefore, we conducted a study to investigate whether the complete implementation of RRT can decrease in-hospital mortality rates and the incidence of unexpected cardiac arrests in the hospital. Materials and Methods: This before-and-after study collected data from a single hospital between January 2014 and December 2019. We evaluated the differences in in-hospital mortality rates and the incidence of unexpected cardiac arrest before and after the complete implementation of an RRT in the hospital. Results: The in-hospital mortality rate [excluding patients with do-not-resuscitate (DNR) orders] decreased from 0.47% to 0.2% after complete implementation of the RRT, achieving a statistically signifi diff Furthermore, the incidence of unexpected cardiac arrests decreased from 0.07% to 0.03% after the complete implementation of the RRT. However, the overall in-hospital mortality rate (including DNR patients) exhibited no statistically signifi diff after RRT implementation. Conclusion: The complete implementation of an RRT did not decrease the overall in-hospital mortality rate but did decrease the in-hospital mortality rate (excluding DNR patients) and the incidence of unexpected cardiac arrests in the hospital.