These files contain data supporting all results reported in Zipple et al. "Transfer to a Naturalistic Setting Restructures Fear Responses in Laboratory Mice". Appropriately classifying a stimulus as threatening or benign depends on a lifetime of novel and dynamic environmental experiences. Animals living in natural environments encounter a wide range of experiences that help them gauge whether a stimulus is threatening. Yet, most behavioral studies of animal anxiety and fear responses are conducted on animals living in laboratory environments that are static and impoverished compared to free-living conditions. In this context, a widely used assay of anxiety behavior—the elevated plus maze—produces a persistent fear response after a single exposure despite being a benign exploration assay. Transferring adult mice from the lab to a large field enclosure mimicking natural mouse environments was sufficient to alter the development of a fear response and recover baseline performance on this anxiety assay. A canonical rodent anxiety phenotype is thus environmentally contingent and rapidly reversible, highlighting the risks of inferring general behavioral principles from impoverished housing conditions.