This study investigates the impact of organizational justice on workplace dynamics, focusing on its cascading effects on workplace loneliness, knowledge hiding, and employee psychological well-being. Drawing on cognitive appraisal theory, we propose that perceived injustice triggers negative emotional responses, such as stress and diminished belonging, which exacerbate workplace loneliness and defensive behaviors like knowledge hiding. Using a time-lagged design with data collected from 333 participants across two phases, our findings reveal that perceptions of injustice significantly influence workplace loneliness, which, in turn, leads to deliberate withholding of information and reduced psychological well-being. The results highlight how feelings of social isolation driven by perceived unfairness disrupt collaboration, diminish innovation, and harm individual mental health. Moreover, our study underscores workplace loneliness as a key mediator, linking justice perceptions to adverse knowledge behaviors and emotional exhaustion. By advancing understanding of the social and emotional mechanisms underlying justice perceptions, this study contributes to the organizational justice literature and provides actionable insights for fostering fair, inclusive, and supportive workplaces to mitigate knowledge hiding and enhance employee well-being.