Purpose : This study examines the dynamic relationships among news-based economic policy uncertainty (EPU), investor sentiment (SI), and herding behavior in the Korean stock market, focusing on the mechanism through which uncertainty is transmitted to collective market behavior via investor sentiment. Research design, data, methodology : Using daily data from 2016 to 2025, the study employs a VAR framework with Granger causality tests, impulse response functions (IRF), and forecast error variance decomposition (FEVD). The EPU and SI indices were constructed as proxy indicators based on news exposure intensity from 13 economic newspapers. Results : Results show no significant linear relationship between economic uncertainty and investor sentiment, limiting the identification of a direct 'Uncertainty-Sentiment-Herding' mediation path. However, sentiment remains a consistent leading predictor of herding behavior even after controlling for uncertainty. This indicates that sentiment acts as an independent transmission channel for market synchronization rather than being a mere byproduct of macro uncertainty. Conclusions : Sentiment is a more critical psychological driver of herding in the Korean stock market than economic uncertainty. It serves as a valid early signal for detecting short-term market crowding. Consequently, policymakers should design sophisticated communication strategies that account for investors' psychological pathways when addressing market uncertainty.