PurposeThe purpose of this study was to test the mediating influence of workplace ostracism in the relationship between organizational cronyism and social capital. In addition, the authors posited that workplace incivility would interact with cronyism to directly influence social capital, and indirectly through its effect on workplace ostracism.Design/methodology/approachUsing data collected in four waves, with a time interval of six weeks between each wave, from 358 university faculty members, the authors used the PROCESS macro to test the proposed moderated mediation model.FindingsResults indicated that workplace ostracism mediates the influence of organizational cronyism on social capital, and that workplace incivility interacts with cronyism to influence social capital directly, and indirectly through its effect on workplace ostracism.Originality/valueMost studies of social capital are theoretical. The few empirical studies have focused on factors that contribute to social capital and virtually no research exists on factors that undermine social capital. Based on the premise that negative interpersonal relationships are far more powerful in explaining outcomes relative to positive interpersonal relations and the notion that “bad is stronger than good,” the authors draw on social exchange theory and the norm of negative reciprocity to test a moderated mediation model and identify a mechanism and the condition under which social capital is undermined. The results have important implications for theory, research and practice.