The term “optimal defaults” refers to imparting pre-selected choices which are designed to produce a desired behavior change. The concept is attractive to policymakers because it steers people toward desirable behaviors while preserving free choice through the ability to opt out. It has been found to be a powerful behavioral determinant in areas such as pension plan enrollment, organ donation, and green energy utilization. We discuss how optimal defaults can be applied to pediatric obesity prevention in several domains including public policy, institutional, private sector, and home environment. Although there are obstacles to overcome in implementing optimal defaults, it is a promising component to incorporate in a multi-level strategy for preventing pediatric obesity.