This study investigates the effect of economic policy uncertainty (EPU) on stock market performance in ASEAN-5 countries using Google Trends data from April 2020 to April 2025. The countries include Indonesia, Malaysia, Singapore, the Philippines, and Thailand. However, EPU indices are not available for all ASEAN-5 countries, therefore, this study develops a Google Trends Uncertainty (GTU) index. The index is constructed from selected keywords drawn from eight economic policy categories to capture online search behavior related to policy uncertainty. Panel data regression analysis was used to examine the relationship between weekly stock returns and GTU index, alongside macroeconomic control variables such as inflation (CPI), exchange rate, interest rate, and growth rate of industrial production index. The results show that GTU index has an insignificant impact on stock returns, implying that markets may not immediately react to rising uncertainty. However, when introducing a one-period lag of the GTU index, the relationship becomes positive and significant. This condition suggests that market responses to uncertainty are often delayed, highlighting slow information absorption and sentiment-driven reactions. Among the control variables, exchange rate and growth rate of industrial production index have significant effects on stock returns, while inflation and interest rates have insignificant effects. This study contributes to the literature on financial markets by employing Google Trends data as an alternative information source for measuring policy uncertainty and highlights the importance of lagged uncertainty indicators in understanding market behavior, especially in emerging markets where access to real-time information may be limited. These findings offer insights for investors, policymakers, and researchers in developing more responsive models and policy frameworks based on digital signals of uncertainty.