A basic assumption about natural hazard policy is risk information will influence risk perception, which will in turn affect individual adaptive behaviors. This paper tests this basic assumption in the context of the National Flood Insurance Program and flood insurance purchasing in San Francisco Bay, California. Using spatially explicit household survey data, we use mediation models to analyze how an individual’s knowledge about which flood zone they live is associated with their flood risk perception and likelihood of purchasing flood insurance. The results suggest that the relationship between risk information, perception, and behavior varies across “risk-informed” who are aware of their flood zone designation versus “risk-uninformed” individuals who are unsure of their flood zone designation. The findings highlight the importance accurately mapping and communicating flood risks in the context of variation in topography, urban structure, and future climate change.