Unpaid volunteers sustain many educational and social organizations, yet evidence on organizational citizenship behavior (OCB) comes mostly from paid employment, where formal roles and material rewards define what counts as extra-role effort. This study tested whether transformational leadership, meaningful work, organizational identification, and psychological capital retain unique associations with OCB when service is unpaid. A cross-sectional survey was completed by 155 active volunteers of Badan Kontak Majelis Taklim (BKMT), an Indonesian federation of Islamic community study groups, recruited purposively from five chapters. Active volunteers were those serving without pay who had completed chapter orientation and had recently taken part in chapter programs coordinated by a chapter leader. The sample met the minimum of 155 required by the inverse square root method to detect a path of .20 with 80% power. Data were analyzed with PLS-SEM (5,000 bootstrap resamples), and the brief measures showed acceptable reliability and validity. The model explained 23.6% of OCB variance. Psychological capital (β = .28, 95% CI [.10, .46]) and transformational leadership (β = .19, 95% CI [.05, .33]) predicted OCB, whereas meaningful work and organizational identification added no unique prediction despite positive zero-order correlations. Among long-serving volunteers, mission meaning and belonging appear to operate as shared conditions for staying, so differences in discretionary effort follow more closely from volunteers' confidence in their own capacities and from leadership support. This pattern marks a boundary condition for the identity and meaning explanations of OCB developed in paid work. Causal and mediation claims remain untested in this cross-sectional design.