When is China prone to miscalculate in international crises? National security institutions—the rules shaping the flow of information between leaders and their diplomatic, defense, and intelligence bureaucracies—offer one important answer to this question. A theoretical framework differentiates between three institutional types: integrated, fragmented, and siloed. Integrated institutions reduce the risk of miscalculation both by building capacity to relay bureaucratic information to the leader, and by fostering a competitive dialogue between bureaucracies that improves the quality of information that they provide. In contrast, miscalculation is more likely under two types of pathological institutions. Fragmented institutions reduce capacity to relay bureaucratic information to leaders and encourage bureaucrats to manipulate information to conform with the leader's prior beliefs. Siloed institutions restrict information sharing between bureaucracies, which degrades the evaluation of information and encourages bureaucracies to manipulate information to suit their organizational interests. A medium-N analysis of China's international security crises from 1949 to 2012 demonstrates that national security institutions help to explain the majority of its crisis miscalculations. Case studies on the 1962 Nationalist invasion scare, the 1969 Sino-Soviet border conflict, and the 2001 EP-3 reconnaissance aircraft incident illustrate the mechanisms by which national security institutions shape the risk of miscalculation in international crises.