The prospect of state and federal laws mandating labeling of genetically engineered (GE) food has prompted vigorous debate about the consequences of the policy on consumer attitudes toward these technologies. There has been substantial debate over whether mandated labels might increase or decrease consumer aversion toward genetic engineering. This research aims to help resolve this issue using a data set containing more than 7800 observations that measures levels of opposition in a national control group compared to levels in Vermont, the only U.S. state to have implemented mandatory labeling of GE foods. Difference-in-difference estimates of opposition to GE food before and after mandatory labeling show that the labeling policy led to a 19% reduction in opposition to GE food. The findings help provide insights into the psychology of consumers' risk perceptions that can be used in communicating the benefits and risks of genetic engineering technology to the public.