Background: Inclusive education of children with intellectual disabilities (ID) is intended to maximize their educational experience within the mainstream school setting. While policy mandates inclusion, it is classroom teachers' behaviours that determine its success. Aims: This study provided a novel application of the theory of planned behaviour (TPB) in this setting. It examined the effect of TPB variables and personality on reported inclusive teaching behaviours for learners with ID. Sample: The sample comprised 145 primary school teachers (85% female) from mainstream schools across Scotland. Method: Participants completed a TPB questionnaire assessing attitudes (instrumental and affective), subjective norms (injunctive and descriptive norms), perceptions of control (self-efficacy and controllability), and behavioural intentions towards using inclusive strategies. The Big Five Personality Index, measuring extraversion, conscientiousness, openness, neuroticism, and agreeableness, was also completed. Teaching practices were reported 2 weeks later. Results: Instrumental attitudes, descriptive norm, self-efficacy, and neuroticism predicted teachers' intentions to use inclusive strategies. Further, conscientiousness had indirect effects on intentions through TPB variables. These intentions, however, did not predict reported behaviour expected by TPB. Instead, self-efficacy was the only significant predictor of reported behaviour. Conclusions: This study demonstrates the application of TPB to an educational setting and contributes to the understanding of teachers' reported use of inclusive strategies for children with ID.