OBJECTIVES: To assess parents’ knowledge and practice about childhood immunization, and to determine the impact of their knowledge and practice on their children immunization status. METHODS: Children immunization timeliness was evaluated using a retrospective cohort study design. The data were collected from ten public clinics in the state of Pahang, the largest state in peninsular Malaysia. Immunization related information was collected from the child’s immunization record card obtained from the parents. Parents’ knowledge and practice was evaluated using a prospective cross-sectional study design by answering validated knowledge and practice questionnaire. Data were analyzed using SPSS version 20.0. Mean and median for the total knowledge and practice score were calculated. Parents’ knowledge and practice was dichotomized into adequate and inadequate using median split method. Chi-square test was used to evaluate the association of parents’ knowledge and practice and their children immunization status. RESULTS: A total of 479 children immunization records were screened and their parent were interviewed in this study. Around two third of the children (63.5%, n=304) had overall age appropriate immunization status. More than half of the parents (54.9%, n=263) had adequate knowledge and practice about childhood immunization. Parents’ knowledge and practice was significantly associated with their children immunization status (p < 0.001). CONCLUSIONS: Understanding parents’ knowledge and practice is an important factor in order to improve immunization timeliness. Educational interventions targeting parents with inadequate knowledge and practice about childhood immunization are needed.