This paper identifies the effects of monetary policy decisions made by the Monetary Policy Board of the Bank of Korea, and examines whether the transmission of monetary policy is asymmetric across business cycle phases. We first employ a narrative approach tailored to the monetary policy environment in Korea, using information considered in the policy decision meetings. With the identified shocks, we estimate local projection regressions to examine not only the overall policy effects but also their asymmetric impacts on the economy across business cycle phases. The results confirm that the monetary policy shocks estimated via the narrative approach effectively capture policy changes and their impacts in a direction consistent with theoretical expectations. For instance, following a contractionary shock, output and inflation decline with some lags. Furthermore, following a contractionary monetary policy shock, macroeconomic variables respond more strongly and rapidly during economic expansions compared to contractions, suggesting that the ‘string theory’ also holds in monetary policy in Korea