Treatment engagement is a vital aspect of a successful course of cognitive behavioral therapy. In this chapter, we review the literature on treatment engagement, considering in-session and between-session metrics including dropout. Acknowledging some role of client characteristics in determining treatment engagement, we look to the literature for indications of therapeutic strategies that facilitate treatment engagement effectively. We highlight evidence for specific therapeutic strategies. New areas for discovery and application are considered. We highlight how the literature on treatment engagement can inform clinical practice.