Author summary Why was this study done? Radical cure with primaquine or recently approved tafenoquine is required to clear the dormant liver parasites of vivax malaria. While single-dose tafenoquine overcomes the barrier of patient adherence to the current 7-day primaquine treatment, it costs more and requires screening for glucose-6-phosphate dehydrogenase (G6PD) deficiency. While the impact of changing policies to tafenoquine after G6PD screening on transmission has been evaluated, the associated costs and cost-effectiveness will be important considerations for policymakers. What did the researchers find? Using an economic evaluation model coupled with a transmission model, we found that prescribing tafenoquine to vivax malaria patients without G6PD deficiency would be highly likely to be cost-effective in Brazil. Tafenoquine will be particularly cost-effective in settings where patient adherence to the current 7-day treatment is low and when paediatric tafenoquine is available