Objectives To evaluate the cost-effectiveness of custom-made insoles compared with general practitioner (GP)-led usual care after 26 weeks of follow-up in individuals with plantar heel pain (PHP) from a societal perspective. Design Cost-effectiveness analysis of a double-blinded randomised controlled trial. Setting General practice in the Netherlands. Participants 116 participants with PHP for at least 2 weeks, aged 18-65 years and presenting to the GP. Interventions Participants were randomised to GP-led usual care (n=46) or referral to a podiatrist for treatment with a custom-made insole (n=70). Participant randomised to a sham insole (n=69) were excluded from this analysis. Primary and secondary outcomes Outcomes comprised pain during rest and activity, and quality of life. Costs included healthcare and lost productivity costs. Statistical uncertainty was estimated using bootstrapping and presented using cost-effectiveness acceptability curves. Results Participants in the custom-made insole group experienced statistically significant more pain during activity at 26 weeks than participants in the usual care group (overall effect 1.06; 95% CI 0.36 to 1.75). There were no significant differences between groups in other outcomes. Total societal costs in the custom-made insole group were non-significantly higher than in the usual care group (mean difference 376; 95% CI-1775 to 2038). The intervention with custom-made insoles was dominated by usual care by the GP (ie, more expensive and less effective) for pain during activity and quality of life outcomes. For the outcome pain at rest, the intervention was more expensive and more effective than usual care. However, the maximum probability of cost-effectiveness was only 0.59 at very high ceiling ratios. Conclusions These findings show that that custom-made insoles are not cost-effective in comparison with GP-led usual care. Clinicians should be reserved in prescribing custom-made insoles for PHP as a primary intervention. Trial registration number NTR5346.