We study the formation of risk perceptions— subjective probability beliefs— of three adverse events—COVID-19 contagion, influenza contagion, and food poisoning—at the onset and outset of the COVID-19 pandemic in the United States, using survey data. We show that perceived risk levels for COVID-19 are similar to those for influenza but are not significantly influenced by proximity to infection and are shaped instead by an individual’s gender, education, and employment status. Using an instrumental variable strategy, we assess whether these perceptions influence a number of protective behaviors. Although risk perceptions are associated with various protective behaviors, we only find a causal impact in increasing the likelihood of phone or online medical consultations by only about a percentage point.