Purpose <p>Accurate perception of food portion sizes is implicated in healthy eating, yet little is known about psychological correlates of portion estimation in non-clinical, normal-weight adults. This exploratory study examined whether consumption intent (self vs other) and markers of psychological processes associated with eating (dietary restraint, shape/weight overvaluation, body dissatisfaction) are associated with portion size estimation errors, and whether these errors relate to body mass index (BMI).</p> Methods <p>Seventy-one adults (BMI 18.5–24.9&#xa0;kg/m²) without current or past psychiatric disorders were included. Eating psychopathology was assessed using the brief 7-item, 3-factor version of the Eating Disorder Examination Questionnaire (Dietary Restraint, Shape/Weight Overvaluation, Body Dissatisfaction). Portion estimation was measured with the Portion Estimation Task, with images rated on a visual analog scale (0–100) under two conditions: general intent (for others) and intent-to-eat (for self). A proportional estimation error index was calculated across all non-full portion sizes relative to each participant’s full-portion reference. A linear mixed model tested the effect of intent and Pearson correlations examined the association with psychological variables and BMI.</p> Results <p>Consumption intent did not influence portion size estimation (<i>p</i> = 0.989), so conditions were combined. Estimation Error Indices were positively correlated with Dietary Restraint (<i>r</i>₍₆₉₎ = 0.27, <i>p</i> = 0.021), but not with Shape/Weight Overvaluation or Body Dissatisfaction. BMI correlated with Shape/Weight Overvaluation and Body Dissatisfaction, but not with Dietary Restraint or the Estimation Error Index.</p> Conclusion <p>In normal-weight adults without eating disorders, greater dietary restraint is associated with larger biases in portion size estimation, whereas BMI and body-related evaluative concerns primarily track weight status rather than perceptual errors in portion size estimations. Findings are exploratory and warrant replication in larger, more diverse samples.</p> <p><i>Level of evidence</i>: III. Evidence obtained from well-designed cohort or case–control analytic studies.</p>