Background: Immunization has averted millions of hospitalizations and deaths from vaccine-preventable diseases. It is a strong public health tool for childhood infection control and prevention. Many mothers are aware of routine immunization but with doubtable knowledge.Objectives: This study determined the mothers/caregivers’ knowledge of routine childhood immunization and vaccination status of their children, aged 12-23 months in Ilorin East Area of Kwara State, Nigeria. It also identified some of the socio-demographic factors associated with good knowledge status of the mothers/caregivers.Methods: This was a community-based cross-sectional study, carried out between December, 2019 and January, 2020, among 456 mothers / caregivers-children’s pairs. Subjects were recruited using multistage cluster sampling technique. Data were collected using a pretested, semi-structured, interviewer-administered questionnaire.Results: Up to 98.0% of the respondents were aware of childhood immunization with healthcare providers (92.1%) being their major source of information. Majority of the respondents (85.3%) had good knowledge of immunization, defined by a score ≤6 out of the 10 questions tested. There was a significant relationship between respondents’ knowledge and full vaccination status of the children (p=0.001). The significant factors associated with good knowledge from binary logistic regression were mothers / caregivers’ age >30 years, antenatal clinic attendance and at least secondary education (OR, p value = 10.60, 0.013; 8.50, <0.001; and 3.98, <0.001 respectively).Conclusion: Mothers / caregivers’ knowledge on immunization was good and this positively affected the full vaccination status of their children. There is a need to sustain female education and encourage antenatal clinic attendance, as tools to improve childhood immunization.