The Person-centred Care Assessment Tool (P-CAT) was developed as a self-reporting assessment scale for staff ratings of the person-centredness of their nursing practice. This study investigates the psychometric properties of P-CAT in a sample of staff working in residential units for older people. Descriptive characteristics were calculated for each item and an independent-sample t-test was used to compare ratings from different groups. Internal consistency and reliability were examined using the Cronbach's alpha coefficient. Exploratory factor analysis was used to evaluate construct validity. Test-retest reliability was examined by means of intra-class correlation and the Pearson correlation coefficient. The mean score of P-CAT was 45.3 (standard deviation 7.8). Cronbach's alpha was 0.83. The factor analysis resulted in a two-component solution organizing the items into two subscales. There were significant differences between ordinary care units and special-care units and between various occupational groups, indicating a discriminating ability of the tool.