Enabling functional communication is critical for accessibility in school and society for all pupils. This systematic review analyzed the results of educational studies on developing communication skills for learners ([less than or equal to]21 years) with autism spectrum disorder and comorbid intellectual disability. Systematic database searches were conducted using ERIC, MEDLINE, and PsycINFO. Seventeen of 208 peer-reviewed articles in English published between 1990 and 2020 met the inclusion criteria. The analysis identified various educational approaches, ranging from using alternative linguistic tools (e.g., signs and gestures) to physical devices (e.g., visual cues), and also examined instructional approaches used by educators. The synthesis shows heterogeneity of methods used, resulting in weak evidence for any model's impact on this pupil group's communication skills development and concomitant possibilities to affect their school situation. In addition, the analysis demonstrated that personnel performance crucially affects children's opportunities to learn regardless of the approach used. Directions for future research are concluded.