This paper examines teachers’ perceptions of their working relationships with learning support assistants (LSAs) when seeking to incorporate young disabled people and pupils with special educational needs (SEN) within mainstream physical education (PE), an area that has been a largely neglected aspect of research in inclusive education. The findings indicate that teachers spoke positively of these relationships when LSAs were perceived as making a positive contribution to the development of pupils’ learning and when they supported teachers as they did in other school subjects. Conversely, when LSAs and other support staff failed to provide teachers with information that was related to pupils’ needs in PE, and when LSAs did not possess the required skills, knowledge and expertise of the subject, teachers were rather critical of their relationships with them. In this regard, LSAs were seen as placing a particularly significant constraint on teachers’ ability to meet the needs of pupils in PE lessons. It is concluded that teachers’ perceptions of the constraints they experience from working with LSAs to help support pupils, and the extent and quality of support they receive, cannot be understood adequately unless they are located within the context of the relational constraints experienced by teachers.