Personalised care is a strategic priority, yet widespread implementation remains slow. Although evidence demonstrates that personalised approaches improve outcomes, experience, efficiency, and equity, healthcare organisations often lack the system-level insight required to understand how personalised care is delivered and what influences its adoption. To address this gap, we developed and tested a comprehensive, system-wide service evaluation tool designed to assess, understand, and monitor personalised care delivery across multiple stakeholder groups.  Drawing on the Consolidated Framework for Implementation Research and underpinned by the COM-B behaviour change model, the tool comprises four mirrored surveys for service users, clinicians, service managers, and system leads. An iterative, exploratory design process, involving service users, public contributors, clinicians, behaviour change experts and system leaders, was used to refine survey structure, content, and usability. The tool was piloted with 24 clinical services across a range of settings; involving 397 service users, 313 clinicians, 73 managers and 40 system leads.    Findings highlight consistent gaps between what staff report delivering and what service users experience, particularly in understanding what matters to people, supporting shared decisions, and offering choice. Although most practitioners felt capable of delivering personalised care, many reported lacking the opportunity—time, resources, prompts and supportive systems—to enact these behaviours routinely. Motivation was generally high, but staff described limited habit formation and few external drivers to reinforce practice. These insights have enabled participating services to identify targeted quality improvement priorities, guided by behavioural determinants, and to plan repeat evaluations.  This evaluation process offers a scalable, theory-informed method for understanding personalised care delivery within complex systems. By generating system-wide insights into behaviours and their drivers, the tool provides a lever for cultural change and sustained improvement. Future work will focus on validation, impact evaluation, and understanding how the tool can support long-term monitoring and transformation of personalised care delivery.