["Journal of the Association for Information Science and Technology, EarlyView. ", "\nAbstract\nThe increasing prevalence of knowledge withholding in online knowledge communities has become a significant obstacle to the growth and development of these platforms. This study explores the influence of social crowding on knowledge withholding with an added focus on the role of individuals' secondary control mechanisms. Experimental results highlight a positive association between social crowding and knowledge withholding that is mediated by four types of secondary control, namely, predictive, interpretive, vicarious, and illusory. Specifically, social crowding increases individuals' perceived loss of knowledge power (interpretive control), knowledge sharing self‐inefficacy (predictive control), and perceived control of information (illusory control) while reducing task visibility (vicarious control), and these factors indirectly contribute to increased knowledge withholding. Results also highlight the moderating role of self‐construal in shaping how secondary control mediates the effects of social crowding. These findings deepen the current understanding of how environmental factors, such as social crowding, impact knowledge withholding and provide valuable insights for community managers seeking to mitigate such behaviors and enhance collaboration within online knowledge communities.\n"]