Introduction <p>Effectivechildhood obesity management requires multicomponent interventions in Primary Health Care (PHC), engaging families, communities, and healthcare professionals to foster healthier behaviors.</p> Objective <p>This study evaluated the effect of a controlled intervention on the nutritional status and ultra-processed food (UPF) consumption of children with obesity receiving PHC services.</p> Methods <p>A randomized clinical trial was conducted with children from PHC units in Betim, Minas Gerais, Brazil. Twenty units were randomly selected and allocated into control (CG) and intervention groups (IG). Children aged 6–10 years with obesity (z-score ≥ +2 for BMI/age) were included. The estimated sample size was 47 per group, considering 20% loss. The IG received monthly activities with four weekly sessions (≥26 contact hours) and five consultations. The CG followed a similar protocol with up to 9 contact hours. Sociodemographic, nutritional, and UPF consumption data were collected through a questionnaire covering 11 food groups. Intention-to-treat analysis compared mean UPF consumption, BMI/age z-score, and BMI (kg/m²) within and between groups post-intervention for a period of 9 months.</p> Results <p>A total of 727 eligible children were identified and 167 were randomized, with 79 assigned to the control group and 88 to the intervention group. Of these, 45 children in the control group and 49 in the intervention group. The intervention significantly reduced UPF consumption in IG at visit 3 [95% CI: -0.95 (-1.87; -0.04)], visit 4 [95% CI: -1.35 (-2.215; -0.49)], and visit 5 [95% CI: -0.94 (-1.83;-0.05)]. No significant differences were found for BMI or BMI/age z-score (<i>p</i>&gt;0.05).</p> Conclusion <p>The intervention effectively reduced UPF consumption. Although no BMI/age reduction was observed, it contributed to weight maintenance and should be considered in PHC childhood obesity strategies.</p> Trial registration <p><i>Clinical Trials</i> NCT05966259 11/09/2023.</p>