© 2017 The Authors. There are marked disparities between indigenous and non-indigenous children's diets and oral health. Both diet and oral health are linked to longer-term health problems. We aimed to investigate whether a culturally appropriate multi-faceted oral health promotion intervention reduced Aboriginal children's intake of sugars from discretionary foods at 2 years of age. We conducted a single-blind, parallel-arm randomised controlled trial involving women who were pregnant or had given birth to an Aboriginal child in the previous 6 weeks. The treatment group received anticipatory guidance, Motivational Interviewing, health and dental care for mothers during pregnancy and children at 6, 12 and 18 months. The control group received usual care. The key dietary outcome was the percent energy intake from sugars in discretionary foods (%EI), collected from up to three 24-h dietary recalls by trained research officers who were blind to intervention group. Secondary outcomes included intake of macronutrients, food groups, anthropometric z scores (weight, height, BMI and mid-upper arm circumference) and blood pressure. We enrolled 224 children to the treatment group and 230 to the control group. Intention-to-treat analyses showed that the %EI of sugars in discretionary foods was 1·6 % lower in the treatment group compared with control (95 % CI -3·4, 0·2). This culturally appropriate intervention at four time-points from pregnancy to 18 months resulted in small changes to 2-year-old Aboriginal children's diets, which was insufficient to warrant broader implementation of the intervention. Further consultation with Aboriginal communities is necessary for understanding how to improve the diet and diet-related health outcomes of young Aboriginal children.