The "Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition" ("DSM-5") diagnostic criteria for intellectual disability (ID) include a change to the definition of adaptive impairment. New criteria require impairment in one adaptive domain rather than two or more skill areas. The authors examined the diagnostic implications of using a popular adaptive skill inventory, the Adaptive Behavior Assessment System-Second Edition, with 884 clinically referred children (ages 6-16). One hundred sixty-six children met "DSM-IV-TR" criteria for ID; significantly fewer (n = 151, p = 0.001) met ID criteria under "DSM-5" (9% decrease). Implementation of "DSM-5" criteria for ID may substantively change the rate of ID diagnosis. These findings highlight the need for a combination of psychometric assessment and clinical judgment when implementing the adaptive deficits component of the "DSM-5" criteria for ID diagnosis.