Body Dysmorphic Disorder (BDD) is a psychological condition in which an individual becomes persistently and excessively preoccupied with perceived defects or flaws in their appearance, even though these flaws are either nonexistent or very minor. This preoccupation leads to anxiety, reduced social functioning, and repetitive behaviors such as frequently looking in the mirror or comparing oneself to others. The present study aimed to determine the effectiveness of Cognitive-Behavioral Therapy (CBT) on appearance anxiety, alexithymia, and self-compassion in girls with BDD. This research employed a quasi-experimental design with a pretest–posttest format and experimental and control groups. The statistical population consisted of girls diagnosed with BDD in Ardabil City in 2024. Based on the inclusion criteria, 36 participants were randomly assigned to either the experimental or control group. The participants were assessed using questionnaires measuring BDD, appearance anxiety, alexithymia, and self-compassion. Following ten 90-minute CBT sessions administered to the experimental group, the participants again completed the study questionnaires. Data were analyzed using multivariate analysis of covariance (MANCOVA) in SPSS-27. The results indicated that CBT significantly increased self-compassion and reduced BDD symptoms, appearance anxiety, difficulty in identifying feelings, difficulty in describing feelings, and externally oriented thinking among adolescent girls (P<0.01). Overall, CBT produced significant reductions in BDD symptoms, appearance anxiety, and alexithymia, while enhancing self-compassion in teenage girls. These findings support CBT as an effective approach for improving psychological aspects associated with BDD.