Background: Families, particularly mothers, play a crucial role in their children's immunization, as they are the basic unit of society and their first point of contact with the world. Methods: This study empirically investigated the family predispositions of immunization: an analysis of the relationship between family disposition and the immunization of children under-5 years in Delta North Senatorial District of Delta State, Nigeria using a well self-structured questionnaires drawn from caregivers of under-5 children who were disposed to immunization in the nine (9) local government areas in Delta North senatorial district of Delta State, Nigeria, which include Aniocha North, Aniocha South, Ika North East, Ika South, Ndokwa East, Ndokwa West, Oshimili South, Oshimili NorthandUkwuani. The questionnaires were distributed to 3843 caregivers across the Nine (9) local government areas in Delta North senatorial district but the researchers were able to successfully retrieve 3624, which constituted about 94% of the sample size. The data from the 94% of the questionnaires were analyzed and presented, which covered socio-demographic details of respondents and family dispositions militating against the immunization of children under-5 years. The hypothesis was analyzed using descriptive statistics (percentage and frequencies) and ANOVA regression analysis to make an inference on the variables usingSoftware Package for Social Scientists (SPSS), version 25. Results:It was found that family disposition is statistically significant in the immunization of under-5 children in Delta North senatorial district of Delta State, Nigeria. Conclusion: It is recommended among others that health facilities should be properly decentralized to different local communities and towns to easy access of mothers (family) for the immunization of their children under-5.