As there is a significant number of Iranian immigrant and illegal refugees living in marginal areas of large cities that might induce immunization gap in these areas. The aim of this study was to provide reliable information on vaccination status of these people. A cross sectional study was conducted on children 24-47 month old who lived in the suburb areas of five large cities of Iran in 2013. Proportional cluster sampling method was used in each city and standard questionnaire of the World Health Organization applied for the purpose of data collection. The survey counts immunizations based on immunization card plus the history of vaccination according to the mother's memory. All gathered data were analyzed using SPSS software (version 16). Overall, 4502 children (49.2% female) aged 24-47 month participated in this survey among which 88.1% were Iranian and 11.9% were Afghan or other nationalities. Totally, 4479 (99.4%, CI 95%: 99.2%-99.6%) of the children had a vaccination card while 828 (18.5%, CI 95%; 15.8%-21.1%) could not present it to the interviewers. 96.8% of children were fully immunized, 3.2% were partially immunized and 0.1% were not immunized. There was no significant difference in terms of vaccine coverage among males and females. The prevalence of partially immunization in non-Iranian children was six fold of Iranian children (11.9% vs. 2%). Immunization program is implemented appropriately with high coverage rates in suburb areas of the country. However, there is still an immunity gap in non-Iranian immigrants, which should be a health system considered as a high-risk group by the health system.