Using the high‐quality intraday transaction data from 2001–2012, we investigate changes in stock market liquidity in response to the monetary policy announcements of the Bank of Korea (BOK). We find that liquidity impairment associated with informed trading occurs prior to the announcements but it disappears subsequent to the global financial crisis. In addition, liquidity impairment appears to become more severe with insufficient experts' predictability and accuracy rather than with policy rate change itself and unscheduled announcements. Finally, the Federal Open Market Committee (FOMC) announcements, changes in the Volatility Index (VIX), and trading by foreign investors play a limited role in explaining stock market liquidity changes. Overall, results indicate that central bank communication plays a significant role in reducing liquidity impairment by enhancing the predictability of policy actions, and therefore, mitigating information asymmetry.