: Anorexia nervosa (AN) is a serious eating disorder associated with several cognitive difficulties including poor cognitive flexibility (i.e. difficulties in effectively adapting to changes in the environment and/or changing task demands). AN research has primarily assessed cognitive flexibility using neurocognitive tests, and little is known about the differences or similarities between self-report and neurocognitive assessments of cognitive flexibility. This study investigated the relationship between self-report and neurocognitive assessments of cognitive flexibility in people with no history of an eating disorder ( = 207) and people with a self-reported lifetime diagnosis of AN ( = 19). Participants completed self-report and neurocognitive assessments of cognitive flexibility through an online study. No significant correlations were found between self-report and neurocognitive assessments of cognitive flexibility for either group of the sample, suggesting that these assessments may evaluate different aspects of cognitive flexibility. Further, negative mood and self-reported eating disorder symptoms were found to significantly relate to self-reported cognitive flexibility, but were not associated with performance on neurocognitive tests of cognitive flexibility.: To provide a comprehensive understanding of perceived and objective cognitive flexibility in AN, future research and clinical assessments should include both self-report and neurocognitive assessments.