Haiti is a low-income country with one of the lowest human development index rankings in the world. Its childhood cancer services are provided by a single hospital with the only dedicated paediatric oncology department in the country. Our objective was to assess the cost and cost-effectiveness of all types of childhood cancer in Haiti to help prioritise investments and to support national cancer control planning. All costing data were collected from the year 2017 or 2018 hospital records. Costs were classified into 11 cost categories, and the proportion of the overall budget represented by each was calculated and converted from Haitian Gourde to United States dollars. The 5-year survival rate was retrieved from hospital records and used to calculate the cost-effectiveness of disability-adjusted life year (DALY) averted, using a healthcare costing perspective. Additional sensitivity analyses were conducted accounting for late-effect morbidity and early mortality and discounting rates of 0%, 3% and 6%. The annual cost of operating a paediatric oncology unit in Haiti treating 74 patients with newly diagnosed cancer was $803,184 overall or $10,854 per patient. The largest cost category was pharmacy, constituting 25% of the overall budget, followed by medical personnel (20%) and administration (12%). The cost per DALY averted in the base-case scenario was $1,128, which is 76% of the gross domestic product per capita, demonstrating that treating children with cancer in Haiti is very cost-effective according to the World Health Organisation Choosing Interventions that are Cost-Effective (WHO-CHOICE) threshold. In the most conservative scenario, the cost per DALY averted was cost-effective by WHO-CHOICE criteria. Our data will add to the growing body of literature illustrating a positive return on investment associated with diagnosing and treating children with cancer in even the most resource-limited environments. We anticipate that these data will aid local stakeholders and policymakers when identifying cancer control priorities and making budgetary decisions.