Background: Cognitive flexibility can be assessed through performance-based tasks and self-report questionnaires, which capture different facets of this construct. Previous research on binge eating (BE) and cognitive flexibility is limited, especially studies combining both assessment methods in Argentine populations. Objectives: This study examined cognitive flexibility in adults with (n = 38) and without BE (n = 23) across assessment methods. We hypothesized that participants with BE would show lower flexibility in self-report measures but not in task-based performance. Methods: 61 adults aged 18-78 years completed an online survey and the Binge Eating Scale, followed by a laboratory session with the computerized Wisconsin Card Sorting Test and the Cognitive Flexibility Scale. Results: A trend-level effect was observed on the ‘Difficulties’ subscale of the Cognitive Flexibility Scale, indicating lower self-reported flexibility in the BE group. No significant differences emerged in other CFS(Total ans Strengths) subscales or WCST indices (RT-errors, perseverative errors and perseverative responses). Conclusions: Findings suggest an association between cognitive flexibility and BE and highlight the relevance of self-report measures, which may better reflect everyday functioning. Combining self-report and performance-based assessments is important for a comprehensive understanding of cognitive flexibility in a more ecologically valid manner.