Individuals with autism spectrum disorder (ASD) and individuals with intellectual disabilities without ASD have limited facial emotion recognition abilities, which may adversely impact social adjustment and other adaptive behavior. This study was designed to examine this relationship in adults with and without ASD. Two groups of adults with intellectual disability, one with a comorbid ASD (n=19) and one without ASD (n=28) completed two facial emotion tasks and two facial non-emotion tasks, each with two experimental paradigms (labeling and matching-to-sample). Social adaptation was measured with the Socialization, Living Skills, and Communication domains of the Vineland Adaptive Behavior Scales, interview edition (VABS; Sparrow, Balla, & Cicchetti, 1983). An ANCOVA with a repeated measures factor for the two tasks with IQ as the covariate found that ASD group scored significantly lower on both emotion and non-emotion facial processing tasks. Hierarchical multiple regression analyses showed that the association between facial emotion processing accuracy and the level of social adaptation was statistically significance for the ASD group only, and that only facial emotion processing accuracy was associated with social adaptation. Limitations of the study are discussed, explanations for the differential findings for the ASD and non-ASD groups are proposed, and implications for intervention are addressed. (Contains 1 figure and 3 tables.)