Quality of relationships is considered a core component of all speech and language therapy work, yet there is little agreement of what constitutes a therapeutic relationship. This study describes a scoping review to map existing evidence that has investigated this in the field of speech and language therapy. The aim of the review was to identify how these relationships were defined, what tools were used to measure them and the key findings of effect of therapeutic relationship on interventions. Using the Joanna Briggs Institute methodology the authors identified 6505 records, which were whittled down to 44 following a screening process. The authors describe that most reports were written in the USA and focused on children or adults with aphasia. Theoretical bases for relationship were mainly related to psychotherapy literature, and terminology use was inconsistent. Studies were both quantitative (17) and qualitative (18). Twelve studies used standardised questionnaires to measure the relationship. Of these, 10 studies reported relationship was a key component to effective therapy outcomes. There is an urgent need for more research to explore both the concept and the importance of relationship in speech and language therapy to enable the development and delivery of effective and relevant interventions across the profession.