Background: Despite the theoretical links between eating disorders and perfectionism, the definition of perfectionism in practice is complicated. The present study explored descriptions and experiences of perfectionism described by a transdiagnostic sample of patients. Methods: In-depth, semi-structured interviews were carried out with 15 patients. The interviews were analyzed by Thematic Analysis. A comparison between the patients' scorings on the Eating Disorder Inventory-Perfectionism scale was also performed. Results: Seven themes were found: The origins of perfectionism, Top performance, Order and self-control, A perfect body, Looking good in the eyes of others, A double-edged coping strategy, and A Sisyphean task. The women in this study did not emphasize weight and body as the main perfectionistic strivings. Core descriptions were instead order, self-control and top performances. All of the participants described the awareness of reaching perfectionism as impossible. Scorings of self-oriented perfectionism was significantly higher compared to socially prescribed perfectionism. No differences in the narratives related to perfectionism scores or eating disorder diagnoses were found. Conclusions: The results showed that psychometric measures do not always capture the patients' definitions of perfectionism, but regarding that perfectionism serves as a means to regulate affects and may lead into an exacerbation of the eating disorder, and the development of obsessive-compulsive symptoms, it is important to investigate the personal definitions of perfectionism.