Background: Immunization is the fundamental public health measure against prevalent pediatric illnesses. However, missed opportunities for immunization may hamper the progress in reducing childhood illness through vaccination Immunization is the safest and effective measure for preventing and eradicating various communicable diseases.

Objective: This study aimed to evaluate the prevalence of MOI among children aged under 5 years.

Methods: A descriptive cross-sectional study was conducted from May 2023 to October 2023 among children under 5 years and their caregivers who were admitted to Primary health care centers in the Thi-Qar city. Data from caregivers was collected using an interview-guided questionnaire.

Results: A total of 425 children and their caregivers were included in this study. 54.1% (n=230) of the children were male while 45.9% (n=195) were female. 13% of children had missed opportunities for immunization in health care centers. 52.7% (n=30) of reasons related to missed opportunities for immunization were associated to the health care provider, followed by reasons related to the child’s caregiver 45.6% (n=26), while the lowest percent was related to the health care center 1.7% (n=1). There were around 45.2% (n=192) of caregivers had a Primary level of education.

Conclusion: The prevalence of missed opportunities for immunization (MOI) in four PHCCs in Thi-Qar city was relatively high. Most reason for MOI was related to health workers. Appropriate policies should not only be developed but also carried out, to make sure that basic health education is available.