The Uganda Learning Hub conducted an in-depth analysis of the country’s immunization data ecosystem to assess the utility of existing platforms in identifying and monitoring zero-dose (ZD) and under-immunized (UI) children. While the DHIS2 remains the primary tool for data capture, its inability to collect individual-level data limits its effectiveness in characterizing ZD children. Emerging platforms such as Smart-Paper Technology (SPT) and the electronic Community Health Information System (eCHIS) offer promising features like unique identifiers and household-level data collection but face challenges with integration, coverage, and sustainability. Findings highlight significant discrepancies in ZD and UI estimates across systems due to variations in data quality, sources, and denominators used. To improve the accuracy of ZD identification and immunization tracking, the study recommends deploying a functional digitalized system at the community level, enhancing data triangulation efforts, and integrating immunization tracking with civil registration systems. These steps are critical to ensuring no child is left behind in Uganda’s immunization efforts.