Anchored in emerging theoretical insights regarding sustainable human resource management, with a focus on pursuing socially responsible HR, we propose that enhancing employees' career satisfaction in public sector organisations constitutes a unique opportunity for public sector organisations to improve their internal social responsibility, focussing on employees as key stakeholders. In this context, this study provides original evidence regarding an original framework for examining the determinants and outcomes of employees' career satisfaction in the US federal agencies, with implications for the internal social responsibility of public sector organisations, which is a dimension of sustainable HR. We use a longitudinal study design involving a sample of permanent, full-time civilian federal employees from two surveys conducted by the US Merit Systems Protection Board. We suggest key factors that affect public sector employees' career satisfaction and aspirations. These key factors may be useful for public sector organisations that wish to design more sustainable and socially responsible HRM centred around the career satisfaction of their internal stakeholders.