Nearly 14% of American preschoolers (ages 2-5) are obese (BMI ≥ 95th percentile for age and gender), yet this group has received little attention in the obesity intervention literature. This review examines what is known about behavioral correlates of obesity in preschoolers and the developmental context for lifestyle modification in this age group. Information was used to critically evaluate existing weight management prevention and intervention programs for preschoolers and formulate suggestions for future intervention research development. A systematic search of the medical and psychological/behavioral literatures was conducted with no date restrictions, using PubMed, PsycInfo, and MEDLINE electronic databases and bibliographies of relevant manuscripts. Evidence suggests several modifiable behaviors, such as sugar sweetened beverage intake, television use, and inadequate sleep, may differentiate obese and healthy weight preschoolers. Developmental barriers, such as food neophobia, food preferences, and tantrums challenge caregiver efforts to modify preschoolers' diet and activity and parental feeding approaches, and family routines appear related to the negative eating and activity patterns observed in obese preschoolers. Prevention programs yield modest success in slowing weight gain, but their effect on already obese preschoolers is unclear. Multi-component, family-based, behavioral interventions show initial promise in positive weight management for already obese preschoolers. Given that obesity intervention research for preschoolers is in its infancy, and the multitude of modifiable behavioral correlates for obesity in this age group, we discuss the use of an innovative and efficient research paradigm (Multiphase Optimization Strategy; MOST) to develop an optimized intervention that includes only treatment components that are found to empirically reduce obesity in preschoolers.