Plurality decisions on the Supreme Court represent extreme dissensus where no clear majority is formed for any one controlling rationale for the final disposition. Studying these decisions is important because they erode the Court’s credibility and authority as a source of legal leadership, and because they provide broader lessons about judicial decision making. This article presents the first systematic analysis of plurality decisions. We test three possible explanations for plurality decisions—a lack of social consensus, “hard” cases, and strategic interactions during opinion writing. We find splintering increases when the Court reviews politically salient and constitutional issues, and when there was dissensus on the lower court, while it decreases when the chief assigns the opinion and when the Court is ideologically heterogeneous.