In patients with colorectal cancer, a trial of a telephone-delivered multiple health behaviour change intervention, using acceptance commitment therapy strategies, found benefits for health and psychosocial outcomes including increased physical activity, improved dietary habits and lower body mass index. Our aim was to address the health economic outcomes by assessing the health system cost and health utility impacts of the intervention. A cost-consequences analysis was performed using data from a two-group randomised controlled intervention trial (n = 410). Outcomes included health-related quality of life (HRQoL), health utility and health system costs. At 12 months, clinically meaningful improvements were found for SF-6D over time but no significant differences were found between groups (P = 0.95). The cost of delivering the 6-month intervention was on average €280 per person and made up 21% of overall healthcare costs for participants during the intervention period. Excluding intervention costs, costs were similar for health professional visits and medications across groups. Despite significant positive intervention effects on health behaviours, health utility and HRQoL scores were similar across groups. On the basis that intervention costs were small and physical activity, diet and weight management improved, on balance the intervention is potentially a worthwhile investment in healthcare funds.