Few weight management interventions target young children with obesity from low-income minority families. To conduct a nonrandomized, pragmatic, pilot study of an adapted, evidence-based, weight management program (Kids N Fitness [KNF]) customized for children ages 3-7 years (Kids N Fitness Jr. [KNF-JR]) on changes in adiposity, nutrition, and physical activity behaviors. One hundred eighty children (ages 3-16) with ≥85th percentile BMI and their parents participated in one of two 6-week weight management interventions dependent on the child's age: KNF-JR: 3-7 or regular KNF: 8-16. Comparisons were made between baseline anthropometrics and health questionnaire responses, and those from weeks 6 to 18. Two-sample tests for equality of proportions with continuity were used to measure proportions of success between KNF-JR and KNF. At week 6, both cohorts showed a mean decrease in BMI z-score (zBMI) of -0.02 ( = 0.3 for KNF-JR [ = 43];  = 0.02 for KNF [ = 59], with no significant group differences. Among program completers, 75% of KNF-JR and 83% of KNF maintained or lowered zBMI at week 18 (within-group difference  < 0.01). On average across all participants, at week 18 vs. baseline, improvements occurred in screen time ( < 0.01 KNF-JR,  < 0.02 KNF), sweetened beverage intake ( < 0.01 KNF-JR,  = 0.03 KNF), physical activity ( < 0.01 KNF-JR and KNF), and water ( = 0.01 KNF-JR, non-significant KNF) and vegetable ( < 0.01 KNF-JR,  = 0.02 KNF) consumption. This pilot demonstrated that an evidence-based weight management program can be adapted for all age groups and results in improved BMI status. Larger, randomized controlled trials are needed to verify effectiveness and sustained impact.