Office chit-chat, as an instant interaction ritual, has widely existed in Chinese organizations and its practical effectiveness has been tested. However, few studies explored the influence of office chit-chat on knowledge concealment and its mechanism. Based on affective event theory and resource preservation theory, we focused on the influence of office chit-chat on knowledge concealment and investigated the chain mediating effect of interpersonal trust—psychological disengagement. Regression analysis using 367 individual samples found that: Office chit-chat has a negative prediction effect on knowledge concealment; Interpersonal trust and psychological disengagement play a mediating role between office chit-chat and knowledge concealment; The chain relation of interpersonal trust—psychological disengagement has a significant mediating effect between office chit-chat and knowledge concealment. The conclusion not only expands the study on the outcome variables of office chit-chat, but also provides a practical reference for organizations to realize the positive effect of chit-chat and tackle employees’ knowledge concealment.