Background: Previous evaluations of community PBS teams have not investigated whether behaviour change is both statistically reliable and clinically significant. Few previous studies have reported quality of life (QoL) and social validity outcomes. Method: The present authors collected data on 85 people referred to a specialist PBS team. The present authors used a unique set of multiple measures and statistical change metrics to evaluate outcome. Results: Statistically significant improvements in QoL and health-related QoL (HRQoL), with medium to large effect sizes, were demonstrated following PBS input. Mean Behaviour Problems Inventory-Short Form scores reduced from 37.74 (SD = 30.54) at baseline to 12.12 (SD = 12.24) at follow-up, with a large effect size (d = 0.84). Stakeholders reported valuing the process and outcomes of PBS, findings which support the social validity of PBS for people with developmental disabilities. Conclusion: This study demonstrates successful PBS outcomes in QoL, HRQoL, challenging behaviour and social validity in a community setting.