BACKGROUND: Children, particularly those who have received no routine vaccinations (zero-dose children), are at high risk of vaccine-preventable diseases in humanitarian crisis settings. However, the decision-making processes underlying vaccine intervention design and delivery in such settings are poorly understood. The present study investigated the decision-making practices of organisations involved in childhood vaccination in humanitarian crisis settings globally via an online survey. METHODS: Individuals involved in the design or delivery of childhood vaccination programmes in humanitarian crisis settings were invited to fill out a self-administered online survey. Respondents were asked about factors influencing intervention design and vaccine delivery; use of technical guidance, specifically the WHO decision-making framework for vaccination in acute humanitarian emergencies (WHO Framework); and practices for reaching zero-dose children. RESULTS: Fourteen responses were received. Large international organisations and UN agencies were overrepresented in the sample. Technical guidance was considered of high importance when designing vaccine interventions. However, the WHO Framework is not available in relevant languages and has not been well-distributed to local and national actors. Awareness of initiatives to reach zero-dose children was high within our sample, though this may not accurately reflect global awareness. Security and resource availability were key barriers to vaccine delivery and reaching zero-dose children. Problems with vaccine access in our sample pertained primarily to issues with the procurement system rather than vaccine cost. CONCLUSIONS: The WHO Framework should be provided in more languages, and vaccination actors at local and national level should be engaged to improve its practicality and increase awareness of its aims. In order to reach zero-dose children, vaccines must be made available for use in expanded age groups, which is sometimes not currently feasible within the Gavi/UNICEF procurement system. Clarifying this policy would allow relevant organisations to reach more zero-dose children. Additionally, security is a key barrier impeding vaccine delivery, including for zero-dose children. Safe operational space for humanitarian actors in conflict must be maintained and global conflict resolution mechanisms improved.