Checking behaviour (CB) occurs in various mental health problems. Cognitive-behavioural models for these mental disorders share similar theoretical assumptions. Thus, they postulate a negative reinforcing effect of CB by reducing negative affect (ie, anxiety) and a maintenance of the pathology due to a lack of reality testing of concerns. This paper details methods for a systematic review that will be conducted to synthesise empirical evidence testing these theoretical assumptions across obsessive-compulsive, generalised anxiety, eating, body dysmorphic and illness anxiety disorder. The results are expected to foster our understanding of the mechanisms of action underlying CB, which is of high clinical relevance. Depending on whether or not the findings confirm the model assumptions regarding CB, the focus of treatments would need to be intensified or modified.