Background: Home environment, modeling of weight-related behaviors, and general parenting style are very important predictors of obesity in children. The effect of parent engagement in prevention of obesity in children is not clear. The main objective of this systematic review was to address the effects of parent engagement in obesity prevention interventions on anthropometric changes among preschool children. Methods: PubMed/Medline, Cochrane Library, ISI Web of Knowledge, Scopus, Science Direct, and Google Scholar were searched. Eligible studies were randomized controlled trials in last 10 years (from 2008 until February 14, 2018), which had a parent engagement in obesity prevention interventions (as an intervention) and children's anthropometric indices (as an outcome). Results: Twenty-six studies were included. Half of studies targeted both parents and children, and the rest targeted only parents. Types of interventions ranged from a simple motivational interviewing to professional skill training approaches. Studies that targeted overweight or obese children in their intervention containing training sessions followed by maintenance for parents and those that focused on individual support for overweight children and their parents, resulted in higher improvement in BMI and other outcomes. Conclusions: Anthropometric indices and BMI are not appropriate for reflecting the effectiveness of parent engagement in obesity prevention interventions. Having an individual component in the intervention and focusing more on parents vs. children in the intervention may result in improvement in anthropometric outcomes. Focusing on weight-related behaviors as the main outcome in both, children and parents, rather than anthropometric indices, is highly recommended for future reviews.