The U.S. regulatory response to the import of potentially contaminated food from Japan following the Fukushima Daiichi nuclear power facility meltdown has not been closely examined. The incident caused global concern about the safety of foods imported from Japan. U.S. scientists and policymakers conducted an initial evaluation of the potential health risks, analyzed information and data from foreign governments and international organizations, adopted an import alert, and conducted extensive monitoring. They did not detect radionuclides in, adopt a ban on, or advise consumers to alter their consumption of foods from Japan. Using a modified Global Simulation Model, National Marine Fisheries Service monthly seafood import data and United Nations trade data, we performed a comprehensive retrospective benefit-cost analysis of U.S. actions on U.S.-Japan trade in fish and seafood. We estimate that U.S. regulatory policy preserved approximately $150 million in annual consumer surplus from the continued import of Japanese fish and seafood (at a cost of less than $1 million for import sampling), while finding no additional exposure to harmful radionuclides. The lesson of our analysis is that investment in regulatory infrastructure has tangible economic benefits, and that retrospective benefit-cost analysis can be a useful framework for evaluating catastrophe risk-related policy strategies.