Objective Anorexia nervosa (AN) is a mental disorder potentially leading to severe malnutrition and life‐threatening complications, with high mortality rates and dropouts from treatment. In the most severe cases, treatment refusal associated with acute nutritional disorders may require compulsory admission in specialised units. The aim of this study was to investigate clinical and nutritional parameters associated with the use of compulsory treatment for severely ill AN patients requiring intensive nutritional care. Methods This retrospective, single‐centre study performed in a unit of specialised nutritional care compared severely undernourished inpatients, compulsorily admitted for AN, with a population of sex‐ and age‐matched voluntarily admitted patients. Socio‐demographic and clinical variables were collected for univariate comparison and logistic regression. Results Compulsory treatment in AN was mainly associated with lower socio‐economic status ( p < 0.01), history of lower weight ( p < 0.05), more frequently prescribed psychotropic medication ( p = 0.02), more previous admissions for AN, longer hospitalisations ( p < 0.01) and binge eating/purging subtype ( p = 0.02). Binge eating/purging subtype and the number of past admissions showed the strongest odds of compulsory treatment in multivariate analysis. Conclusion The knowledge of factors associated with compulsory treatment may help practitioners of all fields to better evaluate its pertinence and indications in AN.