Cognitively oriented therapies, first-line treatment for eating disorders (EDs), still show room for improvement in treatment retention and outcomes. Despite the development of additional cognitive models and therapies, few studies examine the relationship between traditional and third-wave cognitive targets in EDs. The study explores the relationship between irrational beliefs (IBs) and metacognitions and their relationship with ED psychopathology and cognitive reappraisal in ED outpatients. Seventy-seven patients (mean age 27.49 ± 12.28 years) were assessed with The Attitudes and Beliefs Scale-ABS-2, Meta-cognitions Questionnaire-MCQ-65, Eating Disorder Inventory 3-EDI-3, Eating Attitudes Test-EAT-40, Emotion Regulation Questionnaire-ERQ. Correlational analyses showed that IBs and metacognitions significantly correlated with each other. Metacognitions partially mediated the relationship between IBs and ED-related general psychological maladjustment and completely mediated the relationship between IBs and ED symptom severity. Cognitive reappraisal was predicted only by IBs and metacognitions were not significant mediators. While IBs are sufficient in explaining ED-related psychopathology and reduced use of cognitive reappraisal, a potential integration of metacognitions about need to control thoughts in CBT models for EDs may offer incremental validity given their contribution to ED severity. Treatment implications include targeting metacognitions concerning need to control thoughts, as a potential maintenance mechanism of ED symptomatology through cognitive restructuring.