OBJECTIVES:  to assess parents adherence, knowledge, and attitudes on childhood vaccination program among Saudi population METHODS: A cross-sectional study was conducted during November 2016 in Riyadh, Saudi Arabia. Convenient method of sampling was adopted. Parents with children of 0-2 years old were invited to participate. Data was collected through face- to -face interview method using Arabic validated questionnaire to collect demographic data, education level, time of vaccination, adherence, knowledge about childhood vaccination program and attitudes of the parents. RESULTS:  A total of 180 parents were participated. The mother was interviewed in 99 % of cases, Infant’s ages ranged between 2-24 months (mean 10.7 months, standard deviation (SD) 8.2). 28.2 % of sample reported their child is a first child, and this is first exposer to vaccination program. Parents had good adherence to vaccination program ruched up to (87%) on time without delay, main reason for not-adhere to vaccination program was lack of education. On other hand knowledge on aspects related to the general role of vaccination in prevention of some infectious diseases and important of timing of the first dose in vaccination schedule (95.2%), (86.9%). However, poor knowledge was documented among parents in other aspects like the importance of administration of multiple doses of the same vaccine to child immunity (41.6%), administration of multiple vaccines at the same time have no negative impacts on child immunity (47%). The Physicians representing the main source of information for patients about vaccination (77.6 %). Parents attitudes towards immunization was positive, 98% reported the important of vaccination, only 10 % of participants thought that vaccination one of risk factors induced autism. CONCLUSIONS:  Although parents had good adherence, knowledge and positive attitudes on some aspects related childhood immunization, gaps in both studied domains were identified. Educational interventions are needed to upgrade parents’ knowledge.