This study investigated the perception and determinants of caregivers’ participation in immunization in Rivers East Senatorial District, Nigeria. The study adopted the descriptive research design with a population which consisted of three million, nine hundred and thirteen thousand, six hundred and eighty-three (3,913,683) persons in Rivers East Senatorial District. A sample size of 512 was selected using the multistage sampling procedure. Data was collected using a structured questionnaire with a reliability coefficient of 0.75 while analysis was carried out using percentage and chi-square. The result showed that, majority 488(97.6%) of the respondents had positive perception, high level of participation (99.4%). However, no statistically significant relationship was found between participation and other factors such as perception (X2-value = 0.61, df = 1, p>0.05), religion (X2-value = 0.66, df = 2, p>0.05), and age (X2-value = 3.58, df = 4, p>0.05). It was concluded that caregivers in Rivers East senatorial district had positive perception towards immunization and a high level of participation in immunization. It was recommended that, public health practitioners should embark on community based interventions through proper counseling to clear every negative perception about childhood immunization arising from lack of information which influences its participation