Grounded in Conservation of Resources (COR) theory and the resource caravan perspective, this study investigates how workplace bullying reduces organizational citizenship behavior (OCB) through ego depletion. We further propose a moderated mediation model, examining how resilience and perceived psychosocial safety climate (PSC) jointly buffer the effects of bullying on OCB. A two-wave panel study was conducted with a three-month interval, involving 236 employees from various industries in Taiwan. The results reveal that PSC significantly moderates the indirect effect of workplace bullying on OCB via ego depletion. Specifically, the negative link between ego depletion and OCB is strongest when both resilience and PSC are low, but this relationship reverses when PSC is high, regardless of individual resilience levels. These findings highlight the complex interplay of personal and organizational resources in mitigating the adverse effects of workplace bullying on employee prosocial behavior. Theoretical and practical implications are discussed.