This study investigates the effects of shared leadership on counterproductive work behaviors of organizations (CWB-O) and individuals (CWB-I), emphasizing the mediating role of perceived organizational support (POS) across different contexts. Data were collected from 143 organizational teams across three sectors in Tehran, Iran—software, charity, and food production—encompassing 515 team members. Using the social network approach, shared leadership was quantified based on team-level density. Partial least squares structural equation modeling (PLS-SEM) is used to test the hypotheses. The findings revealed that shared leadership significantly reduces both CWB-O and CWB-I, with POS playing a mediating role. Furthermore, findings indicate that team type moderates the relationships between shared leadership, POS, and CWBs. By integrating organizational support theory, social exchange theory, and norm of reciprocity, this study provides a novel theoretical conceptualization linking shared leadership, POS, and CWBs, deepening the understanding of leadership’s impact on workplace behavior.