Background: Immunization is a process of inducing immunity to infection through the administration or introduction of vaccines. However, its coverage is not optimum in most developing countries. The objective of this study is to determine the awareness, perception and coverage of immunization among mothers of under-fives accessing care at the St Charles Borromeo Hospital Onitsha.Materials and Methods: This was a descriptive cross-sectional study involving 300 mothers of under-five children who access immunization services and antenatal care at St Charles Borromeo Hospital Onitsha, Anambra state. A pretested, semi-structured questionnaire was used to collect data. The questionnaire elicited information on the socio-demographic characteristics of the participants, perceptions, attitude and practice of childhood immunization. The participants were interviewed over 5 weeks. The data obtained were analyzed using Statistical Package for Social Sciences (SPSS) version 16 and displayed as percentages.Result: The respondents had a mean age of 28.75 ± 4.44 years. One (0.33%) of the mothers was single while 299 (99.67%) were married and living in a monogamous family setting. All the respondents were Christians, with the majority having completed secondary education 107(35.7%). Majority of the respondents 116(38.67%) were teachers, 94 (31.33%) were traders. The mean age of the children was 2.5±0.6 months. More than half (54.0 %) were females. All the children were delivered in the hospitals where their mothers went for antenatal care. All the mothers said immunization was meant for all children and also that vaccines do not contain contraceptives. Ninety-five percent (95%) of children had received BCG, the remaining 5% were newborns who were about to receive BCG on the day of interview. All the women reported that prevention of deadly vaccine-preventable diseases was the benefit of immunization.Conclusions: Awareness of immunization by the respondents was very high. Majority had good attitude towards immunization. Despite a good uptake of immunization, there were some children who were partially immunized or not immunized at all.Keywords: Immunization, vaccine, perception, under-five, childhoo