There is growing evidence that optimising dietary quality and engaging in physical activity (PA) can reduce dementia and cognitive decline risk and improve psychosocial health and quality of life (QoL). Multimodal interventions focusing on diet and PA are recognised as significant strategies to tackle these behavioural risk factors, however, the cost-effectiveness of such interventions is seldom reported. A limited cost consequence based on a 12-month cluster randomized Mediterranean Diet (MedDiet) and walking controlled trial (MedWalk) was undertaken. In addition, QoL data were analysed. Program costs ($AUD2024) covered staff to deliver the MedWalk program and foods to support dietary behaviour change. The primary outcome measure of this study was change in QoL utility score, measured using the Assessment of Quality of Life (AQoL-8D). Change scores were compared for the groups using general linear models while controlling for demographic factors associated with baseline group differences and attrition. Change in QoL (decreased, maintained, or improved) was determined using a crosstabulation test. MedWalk program costs were estimated at $2,695 AUD per participant and control group cost at $165 per person – a differential cost of $2,530. Mean change in utility scores from baseline to 12-months were not statistically significant between groups. Nevertheless, the MedWalk group was significantly less likely to experience a reduction in their QoL (20.3% MedWalk vs 42.6% control group) (p=.020). A MedDiet and walking intervention may have a role in preventing decline in QoL of older Australians, however, longer term follow up would be beneficial to see if this is maintained.