ObjectiveThe selection of adequate portion sizes plays a key role in the nutritional treatment of eating disorders (EDs). There is limited knowledge concerning the estimation of portion sizes in individuals with EDs.MethodWe performed a systematic review according to the PRISMA statement to synthesise current evidence in this field. Of N = 584 hits, four full‐texts were included in the qualitative synthesis.ResultsWhile patients with anorexia nervosa (AN) tend to overestimate the size of energy‐dense food items and small to medium sized meal portions, they do not show a different estimation compared to healthy controls when judging the amount of food pieces. Large portion sizes were associated with increased anxiety in patients with AN.DiscussionThe overestimation of food portion sizes seems to be driven by attitudinal and/or higher cognitive factors associated with AN. Differences between the studies are discussed and suggestions for future studies are given.