Background: Research on training direct support professionals to address challenging behaviour exhibited by adults with intellectual disabilities is essential in generating effective training approaches for this sector. This systematic review's objective was to evaluate the effects of training types and whether specific training delivery components influenced outcomes. Methods: Following PRISMA (2020) guidelines, 16 single-case design studies were included that directly evaluated behaviour change of service providers training for adults with intellectual disabilities in community settings. Study quality was assessed using Horner et al. ("Exceptional Children," 2005, 71(2), 165-180) criteria. The database searched included Academic Search Complete, CINAHL, Embase, ERIC, Psych Info, and Web of Science. Results: Descriptive analysis of effect size outcomes suggested that all training types were associated with improved outcomes. Further, in situ training was associated with improved service provider performance. Interestingly, feedback was associated with poorer service provider performance. Conclusions: We provide possible explanations for this surprising outcome and propose future research.