To examine the cost-effectiveness of a preventive self-care health management program for community-dwelling older adults as compared to usual care. A cost-effectiveness analysis was executed alongside a randomised controlled trial. Nurse case managers provided interventions, including holistic assessment, empowerment of self-care, preventive health behaviours and self-efficacy with co-produced care planning, supported by nursing students. The control group received social control calls. Community-dwelling older adults were randomly assigned to the intervention (n = 271) or control (n = 269) group. The intervention was conducted in collaboration with 11 community centres under four non-government organisations in various districts of Hong Kong. Cost and quality-adjusted life years (QALYs) were collected pre (baseline, 0months) and post intervention (3months) and 3months after completion of the program (6months). Incremental cost-effectiveness ratios between the groups were calculated, dividing the difference in cost by the difference in QALYs. Analysis showed that the net incremental QALY gain was 0.0014 (3months) and 0.0033 (6months) when the intervention group was compared to the control group. The probability of being cost-effective at 6months was 53.2% and 53.4%, based on the cost-effectiveness thresholds recommended by both the National Institute for Health and Clinical Excellence ($200,000/QALYs) and the World Health Organization (Hong Kong gross domestic product/capita, HK$381,780). The results provide some evidence to suggest that the addition of a home-based, preventive self-care health management program may have effects on cost outcomes for community-dwelling older adults in Hong Kong.