Objective: To describe outcomes from intervention and dissemination of iCook 4-H. Design: Five-state, community-based participatory research and a randomized, controlled trial followed by a 5-state, nonrandomized dissemination test of the iCook 4-H curriculum with control and treatment groups. Setting: Community and university sites. Participants: Youths aged 9−10 years and their adult food preparer; 228 dyads in the intervention and 74 dyads in dissemination. Intervention(s): Theoretical frameworks were Social Cognitive Theory and the experiential 4-H learning model. Six 2-hour, biweekly sessions on cooking, eating, and playing together followed by monthly newsletters and boosters until 24 months, expanded to 8 sessions for dissemination. Main Outcome Measure(s): Youth body mass index (BMI) z-scores, measured height and weight, and youth/adult program outcome evaluations surveys. Analysis: Linear mixed models, group, time, and group £ time interaction for BMI z-score and program outcomes changes. Significance levels = P ≤ .05; interaction term significance = P ≤ .10. Results: In intervention, treatment BMI z-scores increased compared with controls based on significant interaction (P = .04). For odds of being overweight or obese at 24 months, there was no significant interaction (P = .18). In dissemination, based on significant interaction, treatment youths increased cooking skills (P = .03) and treatment adults increased cooking together (P = .08) and eating together (P = .08) compared with controls. Conclusions and Implications: iCook 4-H program outcomes were positive for mealtime activities of cooking and eating together. The program can be successfully implemented by community educators. The increase in BMI z-scores needs further evaluation for youths in cooking programs.