Purpose: Most children who enter out-of-home care (OHC) have been subjected to prolonged maltreatment. Maltreatment potentially contributes to a cumulative deficit in neurocognitive maturation and development that is likely to proceed with the child’s placement into OHC and persist throughout adulthood. From the theoretical perspective of how maltreatment may affect the developing brain, this study examines the IQ and executive function of children placed in OHC on standardized, norm-referenced measures. Furthermore, the study investigates the prevalence of serious cognitive delays, defined by scores in the clinical range on the administered instruments. Methods: The study included 153 children in foster care (66% female), aged 6–15 (M = 10.5, SD = 2.1). Independent two-sample t-tests were run to test for significant differences between the sample and the norm population on the applied neuropsychological measures. Results: The results showed that discrepancies in cognitive development were global in scope, with the children lagging significantly behind the norm population on all applied measures with discrepancies ranging from 0.61 to 2.10 SD (p < .001). Also, serious developmental delays in all cognitive domains were vastly overrepresented in the sample ranging from 11.3% (IQ) to 66.0% (executive function). Conclusions: The results document a very high prevalence of cognitive deficits and delays among the children in the sample. The implications of identifying the neurocognitive effects of maltreatment in the practices of the child welfare system are discussed in terms of developing suitable assessment and intervention strategies.