This is the protocol for a review and there is no abstract. The objectives are as follows: To assess the effects of psychological interventions for the treatment of overweight and obese adults. Specific objectives are to examine the efficacy of: All psychological therapies versus minimal or no intervention; All psychological therapies versus an active diet and/or exercise intervention; Behavioural psychological therapies (first, second or third wave) versus other psychological interventions. Secondary objectives are to examine if the magnitude of intervention effects (objectives 1, 2, and 3) for the primary outcome of BMI are modified by particular intervention characteristics (length of follow-up), or participant characteristics (degree of excess weight). We also plan to investigate whether the effects of behavioural therapy are modified by the type of behaviour intervention (first, second or third wave).