Aim: To investigate factors affecting completion of routine childhood immunization in Riyadh city.

Sample: A convenience sample of 400 parents.

Design: A descriptive cross-sectional correlation design was used to conduct the study.

Sitting: Out-patient waiting areas of the vaccine clinic at King Abdullah Specialized Children’s Hospital.

Tools: Data were collected using four questionnaire sheets included demographic profile, parents’ knowledge regarding childhood immunization, the environment and health services sheet and modified survey of Parent Attitudes about Childhood Vaccines (PACV) sheet.

Results: Nearly half of parents had a Bachelor’ degree. The mean age of the parents was 32.4 years. Nearly half of children were males. Two third of parents were living in urban areas and most of them had a vaccine clinic in their neighborhood. There was a highly significant difference between completion of child's vaccine and parents' knowledge. More than half of the parents were delayed their child’s vaccine. The main reasons for delaying or incompletion the child's vaccine were forgetting vaccine time, sickness of child, inadequate information about the benefit and fear from vaccine side effect. There was a high statistical significance between parents' attitudes, beliefs about safety and efficacy of immunization, the level of hesitancy and the completion of their childhood vaccine.

Conclusion: Parental age, occupation, knowledge, hesitancy in the safety and efficacy of immunizations have been vital and crucial factors affecting the onset and completion of child vaccination; the current study recommended that conduct out an educational intervention study; to support hesitating parents who delayed their childhood vaccination, to improve their behavior towards children Immunization.