The Good Behaviour Game (GBG) is an interdependent group contingency intervention, previously shown to be effective in managing students' behaviour across several studies. An ABAB withdrawal design was implemented to examine the effects of the GBG on the engagement and disruptive behaviours of 12 students diagnosed principally with a mild intellectual disability (M[superscript age] = 7.83 ± 0.83 years) enrolled in two self-contained physical education classes. The first phase of the intervention was carried out from November 27th until Janvier 25th and the second phase took place from April 2nd to May 10th. Video recordings of all sessions were directly observed and analysed using a code unit grid. The collected data were subjected to inferential statistical analysis. Results showed a significant increase in engagement and a decrease in disruptive behaviours during the B1 conditions compared to the baseline A1 for both class 'A' and 'B' (p < 0.001). Similarly, there was a significant increase in engagement and a decrease in disruptive behaviours during the B2 conditions compared to both the A2 and A1 baselines (p < 0.001). Overall, this study demonstrates the effectiveness of the GBG as an intervention for promoting engagement and reducing disruptive behaviours when implemented in physical education settings with students diagnosed with mild intellectual disabilities.