Background: Positive behavioural support (PBS) can be effective in supporting children and young people (CYP) with developmental disabilities. This systematic review focused on describing the components and nine characteristics of PBS that have been used with CYP with developmental disabilities in special education settings, and the evidence for PBS effectiveness in these settings. Additionally, facilitators and barriers to PBS implementation, and experiences of stakeholders, were investigated. Method: Systematic searches followed a registered protocol, and 30 studies were identified, narratively synthesised, and critically appraised. Results: From the 30 studies included, 10 reported the presence of all 9 PBS characteristics, 17 reported on 8 PBS characteristics, and 3 reported on 7 characteristics. Overall, 28 studies demonstrated significant decreases in behaviours that challenge and increases in alternative behaviours, if increasing alternative behaviours was part of the interventions. Conclusions: There was a lack of evidence on facilitators and barriers, and a lack of qualitative studies exploring experiences of stakeholders with PBS in special education settings. The available evidence suggested that not all studies reported on all PBS characteristics when describing the approach followed. In addition, available evidence suggested that most studies demonstrated effectiveness of PBS regarding the measured outcomes. Implications and future directions are discussed.