This article highlights and historically situates three seminal studies on the IQ of adopted children from the 1920s to the late 1940s. It suggests that both researchers’ analysis of IQ in adoption research and agency use of IQ testing were intertwined with intense anxieties about intellectual disability and what it meant for adoptive family building. Agencies utilized mental testing in order to manage the risk of disability in placement and to reassure applicants that their constructed families would be on par with presumed able-bodied, natural ones. Looking at disability in adoption IQ studies and practice provides insight into the shifting notions of disability and family, their constructed and contingent nature, and the practical consequences of their conceptualization.