(1) Background: serious games seem to show promising strategies to promote treatment compliance and motivate behavior changes, and some studies have proven to contribute to the literature on serious games. (2) Methods: this systematic review aimed to analyze the effect of serious games in promoting healthy eating behaviors, effectively preventing childhood obesity, and improving physical activity in children. Five electronic bibliographic databases—PubMed, ACM Digital Library, Games for Health Journal, and IEEE Xplore were used to conduct a systematic literature search based on fixed inclusion and exclusion criteria. Peer-reviewed journal articles published between 2003 and 2021 were selected for data extraction. (3) Results: a total of 26 studies were identified, representing 17 games. Half of the studies tested interventions for healthy eating and physical education. Most of the intervention’s games were designed according to specific behavioral change theories, predominantly the social cognitive theory. (4) Conclusions: studies confirmed the potential of serious games for obesity prevention but considering the restrictions encountered, we exhort for novel designs with different theoretical perspectives.