Background: Despite comparable clinical outcomes, therapists and patients express reservations about the delivery of psychological therapy by telephone. These concerns centre around the quality of the therapeutic relationship and the ability to exercise professional skill and judgement in the absence of visual cues. However, the empirical evidence base for such perceptions has not been clearly established. Methods: We conducted a systematic review to establish what is known empirically about interactional differences between psychotherapeutic encounters conducted face-to-face vs. by telephone. Results: The review identified 15 studies that used situated, comparative approaches to exploring interactional aspects of telephone and face-to-face psychological therapy. These studies revealed evidence of little difference between modes in terms of therapeutic alliance, disclosure, empathy, attentiveness or participation. However, telephone therapy sessions were significantly shorter than those conducted face-to-face. Limitations: We identified only a small number of heterogeneous studies, many of which used non-randomised, opportunity samples and did not use validated measures to assess the constructs under investigation. Disparate therapeutic modalities were used across studies and samples included both clinically diagnosed and non-clinical populations. Conclusions: Available evidence suggests a lack of support for the viewpoint that the telephone has a detrimental effect on interactional aspects of psychological therapy. The challenge for clinical practice is to translate this evidence into a change in practitioner and patient attitudes and behaviours. In order to do so, it is important to understand and address the breadth of factors that underpin ongoing ambivalence towards the telephone mode, which pose a barrier to wider implementation.