Fetal alcohol spectrum disorder (FASD) is a leading cause of neurodevelopmental disorders. Children adopted internationally from countries where alcohol consumption during pregnancy is very high are at greater risk for FASD. Lack of expertise in diagnosing FASD and mixed neurodevelopmental and behavioral signs due to abandonment complicate a timely diagnosis. The aim of this study was to determine the prevalence of FASD in adopted children. Children between the ages of 8 and 24 adopted from Russia and Ukraine were evaluated for clinical and historical features of FASD. Of the 162 children evaluated, 81 (50%) met FASD diagnostic criteria. Thirty-three (20.4%) children had fetal alcohol syndrome (FAS), 28 (17.2%) had partial FAS, 2 (1.2%) had alcohol-related birth defects (ARBD) and 18 (11.1%) had alcohol-related neurodevelopmental disorder (ARND). Of the 81 children in which fetal alcohol exposure could not be confirmed, many had manifestations that would have established a diagnosis of FASD if a history of maternal alcohol consumption was confirmed. In a population of children with a high risk of prenatal alcohol exposure (adoptees from Eastern European countries), at least 50% showed manifestations associated with FASD. The reported prevalence in this study is in line with the results obtained in a previous study as well as in orphanages of origin.