This study explores whether and how exposure to mass media affects regime support in competitive authoritarian regimes. Using geographical and temporal variation in newspaper circulation and radio signal strength in South Korea under Park Chung Hee's competitive authoritarian rule (1961–1972), we find that greater exposure to media was correlated with more opposition to the authoritarian incumbent, but only when the government's control of the media was weaker. When state control of the media was stronger, the correlation between media exposure and regime support disappeared. Through a content analysis of newspaper articles, we also demonstrate that the regime's tighter media control is indeed associated with pro-regime bias in news coverage. These findings from the South Korean case suggest that the liberalizing effect of mass media in competitive authoritarian regimes is conditional on the extent of government control over the media.