JSI worked with UNICEF Nepal and the Kathmandu University Behavioral Science Center to conduct formative research that would inform tailored behavioral interventions aiming to increase vaccination uptake. Using human-centered design and rapid inquiry tools, such as the Behavioral and Social Drivers of Vaccination (BeSD) tool, the research identified the enablers and barriers to vaccination by interviewing the caregivers of fully immunized, under-immunized, and zero-dose children. This brief summarizes the findings and provides recommendations for overcoming the challenges identified.