The aim of the present study was to investigate collaborative memory in adolescents with intellectual disabilities when collaborating with an assistant, and also the extent to which decisiveness is related to individual memory performance. Nineteen students with intellectual disabilities (mean age = 18.5, SD = 0.9) each collaborated with a teaching assistant (mean age 40.3, SD = 12.1) familiar from everyday work in school. Pictures were presented individually. Recognition was performed in two parts, first individually and thereafter collaboratively. The design involved 2 settings, one natural (with equal encoding time) and another with equal individual memory performance (assistants had shorter encoding time than the students). Results showed collaborative inhibition in this previously uninvestigated collaboration setting with adolescents with intellectual disabilities and their assistants. The assistants both performed higher and decided more than the students with intellectual disabilities in the natural setting, but not in the equated performance setting. Inhibition was larger in the equated setting. The assistants' decisiveness was moderately correlated with individual memory performance. Implications for everyday life are discussed. (Contains 2 figures and 2 tables.)