Inclusive education means that all students, including students with disabilities, have the right to access general education classrooms and receive high-quality instruction and appropriate levels of support to enable them to succeed. Given the importance of teacher preparation programs as the first incubator to shape teachers' attitudes towards inclusive teaching practices, there is a need to pay more attention to further studies that focus on preservice teachers' attitudes with considering their level of knowledge and efficacy. The aim of the study is to investigate the relationship between attitudes, knowledge, and self-efficacy of preservice teachers about inclusive practices. This survey used a statistical analysis method performed by collecting data from 108 preservice teachers who were in the teacher preparation programmes at a university located in the Rocky Mountain region and had experience in inclusive classrooms. Analysis found that the preservice teachers' attitudes and knowledge about inclusion contribute to predicting the teachers' efficacy to use inclusive instruction strategies in their classrooms, to collaborate with others, and to manage students' disruptive behaviours. The findings provide information on developing teacher preparation programmes to improve the quality of teaching practices for students with disabilities in inclusive classrooms.