Objectives Health-care costs for the treatment of skin cancers are disproportionately high in many white populations, yet they can be reduced through the promotion of sun-protective behaviors. We investigated the lifetime health costs and benefits of sunscreen promotion in the primary prevention of skin cancers, including melanoma. Methods A decision-analytic model with Markov chains was used to integrate data from a central community-based randomized controlled trial conducted in Australia and other epidemiological and published sources. Incremental cost per quality-adjusted life-year was the primary outcome. Extensive one-way and probabilistic sensitivity analyses were performed to test the uncertainty in the base findings with plausible variation to the model parameters. Results Using a combined household and government perspective, the discounted incremental cost per quality-adjusted life-year gained from the sunscreen intervention was AU$40,890. Over the projected lifetime of the intervention cohort, this would prevent 33 melanomas, 168 cutaneous squamous-cell carcinomas, and 4 melanoma-deaths at a cost of approximately AU$808,000. The likelihood that the sunscreen intervention was cost-effective was 64% at a willingness-to-pay threshold of AU$50,000 per quality-adjusted life-year gained. Conclusions Subject to the best-available evidence depicted in our model, the active promotion of routine sunscreen use to white populations residing in sunny settings is likely to be a cost-effective investment for governments and consumers over the long term.