This paper examines the relationship between parental migration status and child immunization in Southern Ethiopia, a region characterized by high mortality and morbidity. Using the 1997 Community and Family Survey and a multilevel modeling approach, we find that children born to rural–rural migrant mothers have significantly less chance of receiving full immunization coverage than children born to non-migrant mothers. The social mechanism that explains this huge disparity is that rural–rural migrant women have limited social networks in the host community. In addition, significant variation in receiving complete immunization is found by age of child (a likely period effect), mother's education, and distance to nearest health center. Marked child immunization differentials are also observed by ethnicity. The results from the multilevel analysis confirm the persistence of substantial community effects, even after controlling for a standard array of personal and household characteristics. Given the low levels of vaccination among children born to migrant women, health policy interventions and information campaigns might be effectively augmented to reach such migrant women and their children. Community and ethnic group effects suggest that further targeting of health activities could be efficient and effective.