This report from the Uganda Zero-Dose Learning Hub presents findings from a costing study conducted during the 2024 Big Catch-Up campaign. It estimates the incremental costs of identifying and reaching zero-dose and under-immunized children through house-to-house registration and targeted outreaches in three high-burden districts. Results highlight unit costs per child identified and vaccinated, cost drivers, and district variations, offering evidence to guide future planning, budgeting, and sustainability of immunization strategies in resource-constrained settings.