Genuine inclusive education for all students celebrates the diverse abilities, characteristics and capacities of all learners. However, numerous obstacles to inclusion for all students persist, such as differing international conceptions of inclusion. This article explores to what extent British secondary teachers’ belief in inclusive education is related to their level of teacher self-efficacy. The research employs Tschannen-Moran and Woolfolk Hoy’s Teachers’ Sense of Efficacy Scale in examining beliefs towards inclusion and teacher self-efficacy. The study surveyed 122 in-service British secondary teachers; and the results reveal that teachers who believe an inclusive classroom is an effective way to teach all students reported higher levels of teacher self-efficacy than those who did not. The research recommends that relevant supportive professional development aimed towards inclusive education for all is required to build on the attitudes and beliefs of teachers. This in turn will consequently build their level of teacher self-efficacy and classroom practice.