Growing global recognition of the need to monitor healthy ageing has led to frameworks that emphasise maintaining functional ability through interaction between intrinsic capacity and environmental factors. Intrinsic capacity reflects physical and mental capacities, yet psychological capacity remains among the least defined domains and is often measured using deficit-based indicators, limiting understanding of how individuals adapt, cope and maintain function in older age. An International Working Group was convened to develop a working definition, conceptual framework, and key attributes of psychological capacity as part of a broader measure development study. The group comprised 24 experts in intrinsic capacity, gerontology, healthy ageing and measurement development from all six World Health Organization regions. Two virtual meetings were held in late 2025. Discussions were analysed using narrative synthesis to identify key concepts, areas of convergence and divergence. A working definition was developed, describing psychological capacity as the capability to maintain and build functional ability through context-responsive psychological characteristics, assets and skills. Five sub-domains were identified: cognitive appraisal, affect and emotional regulation, adaptability, personal agency, and social competence. In total, 44 attributes were generated. Key challenges included distinguishing psychological capacity from other intrinsic domains, clarifying the role of social components, separating capacity from behavioural or outcome-based measures, and capturing both stability and change across contexts. This work provides a conceptually grounded definition and framework to guide Delphi consensus and measure development, supporting integration of psychological capacity into global monitoring and informing interventions to promote independence and healthy ageing. * We acknowledge the contributions of the International Working Group on Psychological Capacity in Older People.