Introduction: Obesity and overweight are significant health problems among Australian children. Parents play a vital role in establishing healthy eating behaviors in their children. However, parents often experience difficulties in implementing effective parenting practices and lack confidence in their ability to help children adopt these behaviors. This trial will evaluate the efficacy of an online program, Healthy Habits Triple P, in improving children’s snacking and mealtime behaviors and related parenting practices. Methods and analysis: This is a single-blinded, randomized controlled trial for parents of young Australian children aged 2–6 years. Participants will be recruited through childcare centers, social media, online parent forums and existing networks. The participants in the intervention arm will receive access to a web-based parenting intervention in addition to nutrition-related information for parents published by the National Health and Medical Research Council of Australia; those in the control arm will receive nutrition-related information only. After the completion of the study, the parenting intervention will be offered to the control arm. The primary outcome will be improvement in children’s eating habits. The secondary outcomes include parents’ self-efficacy, confidence, children’s mealtime behaviors and mealtime parenting strategies. Both primary and secondary outcomes will be evaluated through online-administered, validated parent-reported questionnaires. We will also undertake a quantitative and qualitative evaluation of the practicality and acceptability of the intervention.