An experimental study investigated the role of sanctioning systems in shaping individual contributions in step-level public good dilemmas. It was predicted and found that procedural justice of the sanctioning system (i.e., accurate vs. inaccurate evaluations of contributions) influenced contributions. Specifically, when group members identified strongly with the group, procedural justice exerted influence only when the group failed in establishing the public good. In contrast, when group members did not identify strongly with the group, procedural justice of the sanction only exerted influence if the group succeeded. These findings suggest that integrating the social dilemma and procedural justice literature may be beneficial for understanding the conditions that determine the effectiveness of sanctioning systems.