This study examined the serving size and energy content per serving of Australian packaged snack foods and confectionery products. Nutrition Information Panel data for 23 sub-categories of packaged snack foods (n = 3481) were extracted from The George Institute for Global Health's 2013 branded food composition database. Variations in serving size and energy content per serving were examined. Energy contents per serving were compared to recommendations in the Australian Dietary Guidelines. Serving sizes varied within and between snack food categories. Mean energy content per serving varied from 320 kJ to 899 kJ. More energy per serving than the recommended 600 kJ was displayed by 22% (n = 539) of snack foods classified in the Australian Dietary Guidelines as discretionary foods. The recommendation for energy content per serving was exceeded in 60% (n = 635) of snack foods from the Five Food Groups. Only 37% (n = 377) of confectionery products displayed the industry-agreed serving size of 25 g. Energy content per serving of many packaged snack foods do not align with the Australian Dietary Guidelines and the industry agreed serving size has not been taken up widely within the confectionery category. Given the inconsistencies in serving sizes, featuring serving size in front-of-pack information may hinder the objective of a clear and simple nutrition message. Messaging to help consumers make healthier choices should consider the variation in serving sizes on packaged snack foods.