Cognitive-behavioural models and interventions for obsessive-compulsive disorder (OCD) have always included some metacognitive elements but until recently these have been predominantly construed of as cognitive as opposed to metacognitive processes. Increasingly, psychological models of OCD are now recognising the importance of metacognitive constructs in the maintenance and treatment of the disorder. Metacognitive models emphasise the importance of thinking processes, and thus represent a step away from traditional cognitive approaches which focused on the content of thoughts. This article reviews the current literature on metacognition in psychological models of OCD with an emphasis on: the role of metacognition in theoretical models of OCD and evidence to support this role; measures of metacognition in OCD; and, metacognitive treatment approaches for OCD and the evidence to support these approaches. The evidence indicates that metacognition has a key role in the aetiology of OCD. Treatment outcome research has indicated promising results, with several trials indicating clinically and statistically significant improvements using metacognitive-based approaches. However, there is a need for larger, controlled trials with longer follow-up periods to improve upon the methodological limitations of studies conducted to date.