This paper examines the relationship between environmental regulatory influence and product innovation in a multi-industry sample of manufacturing organizations. Our theory argues that the influence of environmental regulation on the level of product innovation in a manufacturing organization is at least partially contingent on the organization's internal characteristics—in particular, its structural flexibility and production process flexibility. Hypotheses are derived from our theory and tested, and the results are consistent with the conclusion that structural flexibility and production process flexibility moderate the environmental regulatory influence–product innovation relationship. Whether environmental regulation inhibits or promotes product innovation seems to depend at least in part on certain internal features of an organization. We discuss implications of our results for future organization studies research on environmental regulation, and for research on other types of external constraints on organizational performance.