Healthy ageing relies on maintaining functional ability, shaped by both intrinsic capacity and environmental factors. Psychological capacity, a domain of intrinsic capacity, lacks clear conceptualisation and measurement for monitoring healthy ageing. To address this, an International Working Group held two virtual meetings in late 2025 with 24 experts from six World Health Organization (WHO) regions to develop a working definition and a conceptual framework for measuring psychological capacity in healthy ageing. Using a structured process, the group reviewed the potential attributes and criteria for measurement and proposed the following working definition: Psychological capacity describes all the psychological attributes that contribute to an individual’s functional ability. It comprises intrinsic psychological characteristics, assets and skills that enable the individual to respond to internal stressors and contextual demands. These capacities are expressed as flexible attributes that enable cognitive appraisal, affect and emotional regulation, adaptability, coping, social competence, and personal agency. The resulting definition and conceptual framework provide an important foundation for the measuring and monitoring of psychological capacity in healthy ageing.