Background and Objective: Body dysmorphic disorder (BDD) is characterized by preoccupation with perceived appearance flaws, repetitive checking and avoidance behaviors, and functional impairment. This study examined the effectiveness of a transdiagnostic therapy package in reducing body image concerns and irrational beliefs among women with BDD. Method: This quasi-experimental study used a pretest–posttest design with a two-month follow-up and a control group. Thirty women aged 18–50 years with a clinical diagnosis of BDD were selected through convenience sampling and randomly assigned to intervention and control groups (n=15 each). Diagnosis was confirmed using the Structured Clinical Interview for DSM-5 (SCID-5), psychiatrist evaluation, and the modified Yale–Brown Obsessive Compulsive Scale for BDD. The intervention group received eight 90-minute sessions of a combined transdiagnostic therapy package derived from the principles of Barlow’s Unified Protocol, mindfulness, and schema therapy (not a standard delivery of the Unified Protocol). The control group received no structured intervention. Data were collected using the Body Image Concern Inventory and the Ahwaz Four-Factor Irrational Beliefs Test. Results: The time × group interaction was significant for both outcome variables: body image concerns, F(2,58)=31.80, p<0.001, η²=0.354; and irrational beliefs, F (2,58) =5.90, p=0.018, η²=0.092. Significant reductions in scores were observed from pretest to posttest in the intervention group (p<0.001), and gains were maintained at two-month follow-up. Conclusion: The combined transdiagnostic package, by targeting shared underlying psychological processes, was associated with reductions in body image concerns and irrational beliefs in women with BDD. Because the package has not yet been formally validated, these findings are preliminary.