Employee silence has multiple negative effects on the organization. Studies on the influence of leader negative emotional expression on employee silence are extremely limited, and there are inconsistent findings for the expression of negative emotion among leaders, which highlight the need to explore boundary factors in this field. The purpose of this paper is based on EASI model to examine the impact of leaders’ negative emotional expression on employee silence through the perceptions of psychological safety. Moreover, drawing on social exchange theory, this paper proposed a moderated mediation model to explore how leader–member exchange (LMX) moderates the indirect relationship between leader negative emotional expression and employee silence through perceptions of psychological safety. We employed a bootstrapping technique to analyze the hypotheses. This study adopts two-wave surveys and the results shown that leader negative emotional expression triggered employee silence by employees’ perceptions of psychological safety. This study also demonstrated that LMX weakens the relationship between leader negative emotional expression and employees’ perceptions of psychological safety. Furthermore, LMX weakens the indirect relationship between leader negative emotional expression and employee silence through employees’ perceptions of psychological safety. Using multiphase data collection, we found that when LMX is at a low level, the indirect effect of leader negative emotional expression on employee silence through employee psychological safety is stronger. The theoretical, practical implications and future research suggestions are discussed.