Overweight and obesity are growing health concerns globally. Technological advances drive interest in smartphone applications as possible health behaviour interventions to promote lifestyle change in these conditions. This article critically appraises a Cochrane Review of 18 studies (2703 participants) of smartphone app interventions for overweight or obesity in adolescents and adults and considers its relevance to clinical practice and research. The review’s results suggest that there may be minimal benefit to the use of smartphone apps, but the evidence is very uncertain, lacking high-quality, replicable studies.