Background: Attrition in pediatric weight management negatively impacts treatment outcomes. A potentially modifiable contributor to attrition is unmet family expectations. This study aimed to evaluate the association between adolescent and parent/guardian treatment expectations and attrition. Patients and Methods: A prospective, nonrandomized, uncontrolled, single-arm pilot trial was conducted among 12 pediatric weight management programs in the Children's Hospital Association's FOCUS on a Fitter Future collaborative. Parents/guardians and adolescents completed an expectations/goals survey at their initial visit, with categories including healthier food/drinks, physical activity/exercise, family support/behavior, and weight management goals. Attrition was assessed at 3 months. Results: From January to August 2013, 405 parents/guardians were recruited and reported about their children (203 adolescents, 202 children <12 years). Of the 203 adolescents, 160 also self-reported. Attrition rate was 42.2% at 3 months. For adolescents, greater interest in family support/behavior skills was associated with decreased odds of attrition at 3 months [odds ratio (OR) 0.75, 95% confidence interval (CI) 0.57-0.98, p = 0.04]. The more discordant the parent/adolescent dyad responses in this category, the higher the odds of attrition at 3 months (OR 1.36, 95% CI 1.04-1.78, p = 0.02). Weight loss was an important weight management goal for both adolescents and parents. For adolescents with this goal, the median weight-loss goal was 50 pounds. Attrition was associated with adolescent weight-loss goals above the desired median (50% above the median vs. 28% below the median, p = 0.02). Conclusions: Assessing initial expectations may help tailor treatment to meet families' needs, especially through focus on family-based change and realistic goal setting.