How does codetermination—entitling workers to participate in firm governance, either through membership on company boards or the formation of works councils—affect worker welfare and corporate decision-making? We critically discuss the history and contemporary operation of European codetermination arrangements and review empirical evidence on their effects on firms and workers. Our review suggests that these arrangements are unlikely to significantly shift power in the workplace, but may mildly improve worker welfare and firm performance, in part by boosting information-sharing and cooperation and in part by slightly increasing worker influence.