‘Engaging’ well in psychological therapy is generally associated with more positive clinical outcomes. However, the literature shows little agreement on how to define, conceptualise and measure engagement. Few studies focus primarily on engagement, and those that include engagement measures within other designs rely mainly on single behavioral indicators, such as whether between-session tasks (e.g. ‘homework’ in cognitive behavioral therapy) were completed, or the number of sessions attended. Although pragmatic, I suggest these indicators do not capture the full sense of what engagement means and that taking a broader perspective is likely to be helpful in advancing research and clinical practice. I present a conceptual model of engagement in psychological therapy that aims to draw together relevant theoretical ideas and combine them with observations from clinical practice. This proposes that engagement can be understood as three distinct facets: engagement with the therapist, engagement with the therapy approach, and the practical, behavioural indicators of engagement. I suggest this offers a comprehensive way to conceptualise and understand engagement that may prove helpful for clinicians and researchers. I aim to advocate for further research in this area and for applying the ‘empirically grounded clinical interventions’ approach to therapy processes, not just therapy content. This could help further our understanding of the engagement process, which may play a critical role in driving successful therapy outcomes.