Background: Dairy foods are nutrient rich but also a source of saturated fat in the diets of children. Objective: We assessed effects on dietary intakes and health outcomes of changing dairy foods consumed by children from regular-to reduced-fat varieties. Design: This study was a 24-wk cluster randomized controlled trial in 93 families with 4-13-y-olds who were randomly allocated to parental education regarding changing to reduced-fat dairy foods (n = 76 children) or reducing screen time (n = 69 children). Study outcomes, which were measured at weeks 0, 12 (end of the intervention), and 24, included saturated fat, energy, and nutrient intakes; pentadecanoic acid and blood lipid concentrations; body mass index z score; and waist circumference. Multilevel analyses were used with adjustment for child- and family-level covariates. Results: There were no group differences in overall dairy intakes (-45 g dairy; 95% CI: -141, 51 g dairy; P = 0.356). Saturated fat intakes were 3.3 percentage points lower (P < 0.0001) in the intervention group at week 24 than in the comparison group. Pentadecanoic acid concentrations were lower at week 12 (0.03%; P = 0.012) but not at week 24. LDL-cholesterol concentrations were not different at week 12, but LDL-cholesterol concentration was 0.15 mmol/L lower in the intervention group at week 24 than in the comparison group (P = 0.037). There were no significant group differences in total energy or adiposity measures. Regular-fat dairy foods decreased from 88% to 14% of dairy intake in the intervention group. Calcium, magnesium, and carbohydrate (percentage of energy) intakes were higher in the intervention group than in the comparison group; retinol intakes were lower in the intervention group than in the comparison group; and overall vitamin A intakes were similar between groups. Conclusion: Advice to parents to change to reduced-fat products was effective in reducing children's saturated fat intakes but did not alter energy intakes or measures of adiposity.