<p>This study addresses the lack of mechanism-based explanations linking psychosocial support to customer-related outcomes in service research. Drawing on a systematic literature review using PRISMA and TCCM approaches, the study identifies a persistent fragmentation in the literature, where psychosocial support has predominantly been examined as an antecedent of employee well-being, with limited attention to its role in service performance and sustainability. To address this gap, the study proposes the Psychosocial Service Capability Framework (PSCF), a multi-stage conceptual model that explains how psychosocial support is translated into customer satisfaction through employee service capability and service quality. The framework further incorporates organizational sustainability orientation as a boundary condition that strengthens these relationships. The findings advance the literature by integrating organizational behavior and service management perspectives and by introducing a process-based explanation of value creation in service systems. From a sustainability perspective, the study demonstrates that psychosocial support functions as a strategic relational resource that supports employee resilience, enhances service quality, and contributes to long-term stakeholder value. The PSCF provides a foundation for future empirical research and offers practical insights for organizations seeking to develop sustainable, human-centered service systems.</p>