Purpose: The purpose of this presentation is to share the findings from a research study funded by the National Institute for Health Research Services and Delivery Research Programme. Support workers make up the majority of the workforce in health and social care services for older people. There is evidence to suggest that support workers are not deployed as effectively as possible, are often undervalued, and there are gaps in understanding support worker roles across different care settings. The review was designed to answer the question: how can workforce development interventions improve the skills and the care standards of support workers within older people’s health and social care services? Design: The review was conducted in four iterative stages over 18 months:(1) development of a theoretical framework and initial programme theory; (2) retrieval, review and synthesise evidence relating to interventions designed to develop the support workforce guided by the programme theories; (3) ‘testing out’ the synthesis findings to refine the programme theories, and establish their practical relevance/potential for implementation, and (4) forming recommendations about how to improve current workforce development interventions to ensure high standards in the care of older people. Findings: Eight CMO configurations emerged from the review process, which provide a programme theory about ‘what works’ in developing the older person’s support workforce. The findings indicate that the design and delivery of workforce development should consider and include a number of starting points, specifically; personal factors about the support worker; the specific requirements of workforce development, and the fit with broader organisational strategy and goals. Conclusions: The review has resulted in an explanatory account of how the design and delivery of workforce development interventions work to improve the skills and care standards of support workers within older people’s health and social care services. Contribution: Whilst the theory is specific to our synthesis context of workforce development, we believe the context-mechanism and outcome explanations are sufficiently abstract to be transferable across workforce development in the public services in general.