Applying the 'theory of planned behaviour' to teachers' actions in the classroom, it can be assumed that teachers' positive attitudes towards inclusive education and high self-efficacy beliefs result in an increased use of inclusive teaching practices. However, scientific evidence for this assumption is lacking. This study aimed to investigate factors influencing teachers' use of inclusive teaching practices. In total, 221 (188 female and 33 male) Austrian in-service teachers participated. Participants filled out the attitudes towards inclusion scale (AIS), the Teacher Efficacy for Inclusive Practices Scale (TEIP) and the teacher version of the Inclusive Teaching Practices Scale (ITPS-T). Results showed that teachers had high self-perceptions towards their use of inclusive teaching practices; compared with secondary school, primary school teachers reported using more inclusive teaching practices; there was no difference between expert and novice teachers; teachers' attitudes and self-efficacy were associated with inclusive teaching practices; and self-efficacy predicted teachers' use of inclusive teaching practices.