The metacognition of needing to control thoughts has been implicated in eating disorders (EDs)-specifically, in association with the drive for thinness and over-control. To date, it has yet to be investigated longitudinally in ED outpatients undergoing CBT-based treatment. The current study aims to examine whether endorsing a need to control thoughts undergoes modifications during CBT-based treatment for EDs and whether its modification correlates with treatment response in terms of reduced ED symptomatology. Seventy female ED outpatients (34 with AN, 29 with BN, 7 with OSFED) were assessed at baseline and at the end of treatment with the Metacognitions Questionnaire (MCQ), the Eating Attitudes Test (EAT-40), and the General Health Questionnaire (GHQ). Post-treatment, significant reductions were observed in MCQ-need to control thoughts. Using hierarchical linear regression analyses such decreases significantly explained the variance in observed reductions in EAT-oral control and to a lesser extent, reductions in EAT-bulimia and food preoccupation and EAT-dieting. These results underscore the importance of metacognitive change in EDs and the potential utility of CBT-based treatment in its modification. Improving ED outcomes may warrant broadening the therapeutic target of over-control and a sense of loss of control beyond dysfunctional eating behaviors to include maladaptive metacognitions that concern the need to control thoughts.