Psychological theories propose that evaluations of the consequences of performing a behaviour (attitudes), social influences from other people (norms), and confidence in one’s ability to act (self-efficacy) are the key determinants of people’s decisions and actions. However, the vast majority of studies only measure associations between these variables and so it is not clear whether changing people’s attitudes, norms, or self-efficacy will cause changes in their subsequent intentions or behaviour. The present research reviews intervention studies that were successful in changing these key predictor variables in order to determine how big an effect these changes have on subsequent motivation and action. Computer-based literature searches are used to identify published and unpublished intervention studies, and meta-analysis is used to quantify the extent to which cognition change engenders intention and behaviour change. Moderator analysis is used to examine conceptual and methodological factors that determine the strength of observed effects. The review will also identify characteristics of interventions that were most successful in changing attitudes, norms, or self-efficacy. This information will then be used to design and test a “best practice” intervention to promote intention and behaviour change. Thus, the present research provides a critical test of psychological theories of motivation and action.