OBJECTIVES Our aim was to compare the effect of 2 treatment models on attendance and child weight status: a less intense guided self-help (GSH) program delivered in the primary care setting versus traditional family-based behavioral treatment (FBT) delivered in an academic center. METHODS We conducted a randomized clinical trial among 164 children between 5 and 13 years old with a BMI ≥85th percentile and their parents. The intervention group (GSH) received 14 individual sessions over 6 months, with 5.3 hours of treatment. The control group (FBT) received 20 group-based sessions over 6 months, with 20 hours of treatment. Main outcomes included proportion of sessions families attended and change in child BMI z-score (BMIz), percentage from the 95th BMI percentile, difference from the 95th BMI percentile at the end of treatment, and 6-month follow-up. RESULTS Mean age of children was 9.6 years, BMI z-score 2.1, 49% female, and >90% Latino. The odds of attending GSH compared to FBT was 2.2 (P < 0.01). Those assigned to GSH had a 67% reduced risk of attrition (hazard ratio = 0.33, 95% confidence interval 0.22–0.50, P < .001). Intent-to-treat analysis showed no between-group differences in change in BMIz and percentage from the 95th BMI percentile over time. Combined, there was a significant reduction in BMIz from baseline to posttreatment (β = −0.07 (0.01), P < .01, d: 0.60) and a slight increase from posttreatment to follow-up (β = 0.007 (0.13), P = .56). CONCLUSIONS This study provides support for a novel, less intense GSH model of obesity treatment, which can be implemented in the primary care setting. Future studies should examine effective approaches to dissemination and implementation of GSH in different settings to increase access to treatment.