The Republic of Korea (ROK) experienced a public health crisis due to the Middle East respiratory syndrome (MERS) in 2015 and is currently going through the coronavirus disease 2019 (COVID-19) pandemic. Lessons learned from the disastrous MERS outbreak were reflected in the preparedness system, and readiness made since then enabled the country to successfully flatten the epidemic curve of COVID-19 in late February and March 2020. In this review, we aimed to summarize and compare the epidemiology and response of ROK to the 2015 MERS outbreak and the COVID-19 epidemic in early 2020. We emphasize that given the next waves seem inevitable, it is urgent to develop comprehensive preparedness and response plans against the worst scenarios of COVID-19 pandemic. Simultaneously strengthening healthcare capacity to endure the peak demand and smart strategies to sustain social distancing and public hygiene are necessary until the effective and safe therapeutics and vaccines against COVID-19 are available.