The current study investigated the effects of a behavioral intervention plus laxative therapy for 2 adolescents with Autism Spectrum Disorder (ASD), Intellectual Disability (ID), and chronic histories of constipation and frequent fecal accidents. The treatment consisted of regularly scheduled toilet sits, an incentive system for bowel movements in the toilet, and a cleanup procedure for fecal accidents, plus a laxative. The behavioral intervention was implemented at home by each participant’s parents and at school by educational staff. A multiple baseline design across participants was used to evaluate the effects of the treatment on participants’ frequency of soiling, frequency of successful bowel movements in the toilet, and successful self-initiated bowel movement in the toilet. The treatment resulted in improvements in both participants’ fecal incontinence. Specifically, both participants achieved full fecal continence after 9 and 10 weeks respectively. Moreover, treatment gains were maintained following the withdrawal of the behavioral intervention and laxative. Results indicate that a behavioral intervention implemented across settings and laxative therapy can have a profound effect on the encopresis of adolescents with co-occurring ASD and ID.