This article identifies the factors that characterise effective interpersonal partnerships between teaching assistants (TAs) and teachers working in inclusive schools in Catalonia (Spain). This phenomenological study, based on 40 semi-structured interviews with 22 TAs and 18 teachers revealed that the main interpersonal factors affecting partnerships were: feeling at ease; trust; respect; and valuing one another. Participants detailed key aspects such as personal affinity, professional compatibility, open communication, a sense of belonging to a class-group, and teamwork, as additionally important for successful partnerships. The findings provide insight into how schools can support the development of effective TA-teacher partnerships. Implications are discussed.