BACKGROUND: Economic evidence on the long-term benefits of investing in early childhood development is limited. This study aimed to estimate the potential long-term economic benefits of an early childhood development intervention 'Learning Clubs' in Vietnam. METHODS: We conducted a cost-benefit analysis to estimate the costs and benefits of the intervention compared to the standard of care from a limited societal perspective. The intervention cost and child cognitive development outcome were derived from the published 'Learning Clubs' trial-based cost-effectiveness analysis. Benefits were monetised based on the gains in wages associated with improved cognitive development over a lifetime at the population level, using a life-table model. The benefit-cost ratio was estimated as the benefits in wages divided by the intervention cost with a 3% discount rate, assuming nationwide scale up to a hypothetical national birth cohort. Sensitivity, scenario, and threshold analyses were conducted to examine the uncertainty around the model. RESULTS: The benefit-cost ratio was 5.52, indicating that the expected benefit for each US invested would be US.52. The intervention would generate economic benefits of US,566 per child over their lifetime. Upon nationwide scale-up, the total benefit would amount to US.28 billion per national annual birth cohort. Probabilistic sensitivity analyses estimated the benefit-cost ratio to be 5.90 (95%CI 2.66 to 11.12). The findings were relatively robust as the benefit-cost ratios remained above 1 in all sensitivity and scenario analyses. CONCLUSIONS: Our findings support greater investments in early childhood development. The Excel-based model is available for further use and adaption to other settings.