Therapist adherence is a component of treatment integrity pertaining to whether activities in psychotherapy are aligned to the intended treatment approach. It is important to establish what occurs during the course of psychotherapy so that determinations of treatment efficacy can be made accurately. Studies suggest that treatments are distinguishable by ratings made using measurement tools designed to measure therapist adherence. Mixed findings are reported in the literature as to what happens to adherence over the early, middle and late phases of psychotherapy. Ratings of three therapy sessions from participants (n = 112) who completed a randomised clinical trial comparing cognitive behavioural therapy, appetite focused cognitive behavioural therapy and schema therapy for transdiagnostic binge eating comprises the data for this study. Two hypotheses were generated. Firstly, that the three therapy types would be distinguishable by raters blind to the treatment participants were assigned to. Secondly, that the rating scores of two therapy non-specific subscales will be comparable across the three therapy types. An exploratory analysis was undertaken to examine adherence across the early, middle and late stage of therapy. Results indicate that therapy type was distinguishable by mean subscale rating scores and that the non-specific subscales were comparable regardless of treatment randomisation. The exploratory analysis indicated that there were differences in adherence across phase for the whole sample, with differences in the cognitive behavioural therapy and appetite focused cognitive behavioural therapy subscales, but not the schema therapy subscale. No significant phase by therapy effects were found. Understanding what occurs in psychotherapy informs treatment delivery and has potential to improve outcomes for those with eating disorders.