Issue addressed Portion size guidance strategies have been suggested as an important component of weight management; therefore, the Health Star Rating (HSR) front-of-pack labels could influence consumers' portion-size decisions. However, this has not been investigated to date. This study aims to evaluate whether presenting energy content information and HSRs influences portion size self-selection of specific foods and meals. Methods Adults were randomly assigned to one of three experimental groups in this randomised controlled experiment. Each participant was given either a kJ/100g food label or a HSR label, or was given no information on nutrient composition. They were then asked to serve themselves an adequate portion of breakfast cereal (Kellogg's Nutri-Grain), fruit salad and chocolate, plus a three-component meal (chicken, fries and mixed vegetables). Portion serves and meal weights were compared between each experimental group using ANOVA and the discretionary foods were also compared with the Australian Guide to Healthy Eating (AGHE). Results Neither the kilojoule nor HSR information influenced the self-served portion size of foods or meal components. Mean self-served portion size of the discretionary foods were significantly greater than the standard serving sizes as specified in the AGHE. Conclusion Although food labels have the potential to assist consumers in making product choices, this study indicates that presenting nutrition information does not affect portion size decisions in young adults. So what? Strategies that assist consumers to choose appropriate portion sizes should be developed as a weight management tool.