Aim:To assess the internal reliability and validity (content and criterion) of the Older Patients in Acute Care Survey (OPACS) as a measure of nurses' knowledge, attitudes and practices regarding care of older hospitalized patients in Australia. Design:Cross-sectional survey. Method:A convenience sample of final year nursing students at an Australian university in October 2014 completed the OPACS (N = 191). Internal reliability was assessed using Cronbach's alpha, content validity using exploratory factor analysis and criterion validity using correlations between the OPACS and Palmore's Facts on Aging Quiz and the Caring Efficacy Scale. Results:Despite good internal reliability on both OPACS subscales, exploratory factor analysis of the 36 items representing behaviours and the 50 items on knowledge and attitudes failed to load strongly on their corresponding factors. Analyses of criterion validity suggested the OPACS scales are measures of attitude.