Background: In Japan, cognitive behavioral therapy (CBT) for panic disorder (PD) is not well established. Therefore, a feasibility study of the clinical effectiveness and cost-effectiveness of CBT for PD in a Japanese clinical setting is urgently required. This was a pilot uncontrolled trial and the intervention consisted of a 16-week CBT program. The primary outcome was Panic Disorder Severity Scale (PDSS) scores. Quality of life was assessed using the EuroQol’s EQ-5D questionnaire. Assessments were conducted at baseline, 8 weeks, and at the end of the study. Fifteen subjects completed outcome measures at all assessment points. Results: At post-CBT, the mean reduction in PDSS scores from baseline was −6.6 (95 % CI 3.80 to −9.40, p &lt
0.001) with a Cohen’s d = 1.77 (95 % CI 0.88-2.55). Ten (66.7 %) participants achieved a 40 % or greater reduction in PDSS. By calculating areas under the curve for EQ-5D index changes, we estimated that patients gained a minimum of 0.102 QALYs per 1 year due to the CBT. Conclusions: This study demonstrated that individual CBT for PD may be useful in Japanese clinical settings but further randomized control trials are needed.