Background: Patients with adolescent idiopathic scoliosis (AIS) under brace treatment perceive stress, not only from scoliosis, but from wearing the brace itself. The Bad Sobernheim Stress Questionnaire–Brace (BSSQbrace) was developed to assess the level of psychological stress induced by brace treatment for AIS. However, a Japanese version of BSSQbrace had not yet been developed. Methods: We developed a Japanese adaptation of the Bad Sobernheim Stress Questionnaire–Brace (JBSSQ–brace) through a guideline-based process to adapt assessment of the psychological effect of brace treatment for AIS in Japanese patients. We administered the JBSSQ-brace to 71 patients with AIS under brace treatment in our clinic. Internal consistency and reproducibility were analyzed using Cronbach's alpha and a test–retest method. Results: We included 44 patients that responded adequately. JBSSQ–brace achieved excellent internal consistency (Cronbach's alpha = 0.84 for the first questionnaire, and 0.87 for the second) and substantial reproducibility (interclass correlation coefficient = 0.75). The average score for JBSSQ–brace was 16.5 and 16.8, and almost 40% of AIS patients felt a moderate-to-high stress from brace treatment. Conclusions: JBSSQ–brace is an effective instrument with which to evaluate the stress level from brace treatment in Japanese patients with AIS.