AIMS AND OBJECTIVES: To construct and evaluate an intervention tool for increasing the person-centredness of care in residential aged care services. BACKGROUND: Providing care that is person-centred and evidence-based is increasingly being regarded as synonymous with best quality aged care. However, consensus about how person-centred care should be defined, operationalised and implemented has not yet been reached. DESIGN: Literature reviews, expert consultation (n = 22) and stakeholder interviews (n = 67) were undertaken to develop the Tool for Understanding Residents' Needs as Individual Persons (TURNIP). METHODS: Statistical estimates of validity and reliability were employed to evaluate the tool in an Australian convenience sample of aged care staff (n = 220). RESULTS: The 39 item TURNIP conceptualised person-centred care into five dimensions: (1) the care environment, (2) staff members' attitudes towards dementia, (3) staff members' knowledge about dementia, (4) the care organisation and (5) the content of care provided. Psychometric testing indicated satisfactory validity and reliability, as shown for example in a total Cronbach's alpha of 0·89. CONCLUSIONS: The TURNIP adds to current literature on person-centred care by presenting a rigorously developed intervention tool based on an explicit conceptual structure that can inform the design, employment and communication of clinical interventions aiming to promote person-centred care. RELEVANCE TO CLINICAL PRACTICE: The TURNIP contains clinically relevant items that are ready to be applied in clinical aged care. The tool can be used as a base for clinical interventions applying discussions in aged care organisations about the quality of current care and how to increase person-centredness of the care provided.