Using critical incident technique (CIT) and grounded theory, this paper explores the fellow customers’ reaction to customer misbehavior. Through in-depth interview, 232 customer misbehavior incidents are collected, and then CIT is used to categorize fellow customers' reaction patterns. Based on this, this paper discovers the antecedents of different reaction patterns. The finding suggests five types of fellow customers’ reaction patterns: helping the jaycustomer, mimicking the misbehavior, looking on indifferently, stopping the misbehavior, and giving himself up to help others. Five reaction patterns are quite different in frequency, motive, performance, and influence on five involved agents. The features of jaycustomer, focal customer, other fellow customers, employee and firm, will determine the choice of focal customer, through the intermediary effect of two mediator variables, that is, expectation of interaction consequence, and judgment on interaction responsibility. From the perspective of fellow customers' interaction, this paper not only enriches the literatures on customer misbehavior, but also provides managerial implication for customer misbehavior management and employee training program.