A growing number of childhood obesity interventions involve children and youth in participatory roles, but these types of interventions have not been systematically reviewed. We aimed to identify child and youth participatory interventions in the peer-reviewed literature in order to characterize the approaches and examine their impact on obesity and obesity-related lifestyle behaviours. We searched PubMed/Medline, psychINFO and ERIC for quasi-experimental and randomized trials conducted from date of database initiation through May 2015 that engaged children or youth in implementing healthy eating, physical activity or weight management strategies. Eighteen studies met our eligibility criteria. Most (n = 14) trained youth to implement pre-defined strategies targeting their peers. A few (n = 4) assisted youth to plan and implement interventions that addressed environmental changes. Thirteen studies reported at least one statistically significant weight, physical activity or dietary change outcome. Participatory approaches have potential, but variation in strategies and outcomes leave questions unanswered about the mechanisms through which child and youth engagement impact childhood obesity. Future research should compare child-delivered or youth-delivered to adult-delivered health promotion interventions and more rigorously evaluate natural experiments that engage youth to implement environmental changes. With careful attention to theoretical frameworks, process and outcome measures, these studies could strengthen the effectiveness of child and youth participatory approaches.