The effectiveness of Sexual Offending Treatment programmes has generally been measured through evaluating intervention content and reoffending rates. In response to the growing call to explore the role of therapeutic process in facilitating meaningful change on these programmes, this thesis considers how interpersonal dynamics may influence programme effectiveness from the perspective of the group member. This offers the opportunity to consider the impact of how we work, rather than what we do. The critical literature review uses a pluralistic framework to present relevant existing research and identify gaps in practice-based knowledge in the field of sexual offending intervention from a Counselling Psychology perspective. While the literature suggests interpersonal ingredients important to this process, it offers little information regarding where, when and how these qualities are effective. Furthermore, little is understood about the impact of relational dynamics between the facilitators and group members in creating a facilitative environment. This reveals broad gaps in research relating to a neglect of the client’s experience of these interactions and how they are conceptualised in their change process. This research therefore uses a social constructivist grounded theory method to generate data exploring these process issues. The results highlight the value of facilitators fostering a dynamic and balanced core interpersonal process that is sensitive to the unique context of these group interventions. This offers a foundation for group member engagement and effective group functioning relevant to subjective change. The implications for theory and practice are discussed, highlighting how a Counselling Psychology presence in this field has the potential to enhance practice. The study is concluded with reflections of the study’s limitations and areas in need of further research.