Data from Norway were analyzed to evaluate early behavioral intervention for children with intellectual disabilities. The intervention group (n = 11) received approximately 10 hours per week of behavioral intervention; the eclectic comparison group (n = 14) received treatment as usual. After 1 year, changes in intelligence and adaptive behavior scores were statistically significant in favor of the behavioral intervention group (effect sizes of 1.13 for Intelligence quotient (IQ) change and 0.95 for change in adaptive behavior composite). Approximately 64% of the children in the behavioral intervention group met objective criteria for reliable change in IQ, whereas 14% in the eclectic comparison group did so. These results suggest that children with intellectual disability may profit from behavioral intervention typically provided for children with autism. (Contains 1 table and 1 figure.)