Obsessive-compulsive disorder (OCD) and related disorders such as body dysmorphic disorder (BDD) can take many different forms of presentations. The term ‘complex’ is common and inconsistently used in both OCD and BDD. Practitioners often refer to complex OCD or BDD when patients present with severe co-morbid problems, often in the context of personality difficulties, dissociation, difficult early relationships and trauma; or when the illness is chronic and debilitating with previous multiple treatment failures. Current best-evidence treatment protocols for both disorders focus heavily on exposure and response prevention (E/RP) but with moderate success, particularly in patients who are deemed ‘complex’, and often those with relevant shame and/or disgust-based past experiences. The aim of the present paper is to (a) describe factors that contribute to complexity in OCD and BDD, and (b) link these with theory and practice. We emphasize the importance of understanding both the function of OCD and BDD-related behaviours (rather than the content of obsessions or compulsion), and the context in which they occur such as the family. We illustrate complexity in OCD and BDD using real case material, using a functional and contextual approach to formulate the client's difficulties, and demonstrate how E/RP can be enhanced successfully with imagery rescripting, family work, and compassion-focused therapy.