Purpose-Vaccine preventable diseases are major threats to the health and well-being of children under five years of age. They contribute a great deal to childhood illnesses and disabilities, and are accountable for a high percentage of childhood mortality worldwide. In Nigeria, the government has made a lot of effort to provide immunizations against these childhood diseases. It is however sad to note that many children still do not complete their routine immunization. The purpose of this paper is to determine factors which influence mothers' compliance with childhood immunization. Design/methodology/approach-This was a descriptive study carried out among 600 mothers of under-five children randomly selected from nine postnatal clinics in Ekiti State between January and August 2016. A self-structured validated questionnaire containing items to explore demographic characteristics of respondents, compliance with child immunization (Cronbach's α ¼ 0.92) and determinants of compliance (Cronbach's α ¼ 0.83) was the instrument for data collection. Multiple regression analysis was used to identify determinants of mothers' compliance with childhood immunization. Findings-The level of compliance of mothers with childhood immunization was high (80 percent). The two factors which contributed significantly to mothers' compliance were the mothers' knowledge of childhood immunization (β weight ¼ 0.243) and mothers' educational status (β weight ¼ 0.169). Mothers with tertiary education had the highest level of compliance (76.8 percent). Originality/value-Having good knowledge of childhood immunization and a high educational status positively influence a mothers' compliance with child immunization.