Childhood obesity is a high prevalence condition that causes a high burden of disease in adulthood. Mobile phone app are increasingly used to prevent it. We summarized the evidence on the effectiveness of mobile apps for devices used by parents to prevent and treat childhood and adolescent obesity. An update of a systematic review of the literature (De Lepeleere et al., 2017) was carried out. PubMed, Embase, Cochrane, CINAHL, PsycINFO, Scopus, and ERIC were searched up to 2020. The included studies should target children 1-18 years, compare an app aimed at preventing or treating overweight and obesity, as stand-alone intervention or as part of a complex program, installed on parents' mobile devices, to no intervention or an intervention without the app. Outcomes related to weight status, diet, and physical activity (PA) behaviors were considered. Nineteen studies (14 RCTs and 5 non-randomized trials) were included. The app was mainly used to record food consumption and PA, to set goals, to view progress, and send health promotion messages. One study reported a significant decrease and one a suggestive decrease in anthropometric measures in obese and overweight children, while other studies observed no effect. One study reported a significant increase in PA. Six interventions proved to be effective in changing dietary behaviors. Interventions targeting overweight and/or obese children had the most positive results. All studies reported high acceptability and feasibility of interventions. The differences between interventions and the small sample size of the studies did not allow this review to reach conclusion on effectiveness.