Self-induced vomiting is adopted by people with a variety of eating disorders (ED) to control body shape and weight. We tested the prevalence, the associated features and the role on treatment outcome of self-induced vomiting in 152 ED patients consecutively admitted to an inpatient cognitive-behavioral treatment (CBT), based on the transdiagnostic CBT for ED. The Eating Disorder Examination, together with the Beck Depression Inventory, the State-Trait Anxiety Inventory and the Temperament and Character Inventory were recorded at entry and at end of treatment. Self-induced vomiting was reported in 35.5% of cases, and 21.1% had multiple purging with vomiting. Individuals with vomiting and those with multiple purging had significantly higher BMI and a higher frequency of bulimic episodes, but individuals with multiple purging were also characterized by higher levels of depression, longer ED duration, more severe ED psychopathology and lower self-directness. Individuals with vomiting had higher eating concern and novelty seeking compared with those without purging behaviors. However, the three groups had similar dropout rates and outcomes in response to inpatient CBT, in keeping with the transdiagnostic theory of EDs.