Objective The Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN) is a scale used to clinically evaluate disturbances in biological rhythm. In this study, we aimed to examine the reliability and validity of the Korean version of the BRIAN (K-BRIAN) in a Korean population. Methods A total of 181 participants, including 141 outpatients with bipolar disorder (BD; type I, 62; type II, 79) and 40 controls, were recruited. Construct validity was tested by comparing the mean K-BRIAN scores of the BD patients and control subjects. Concurrent validity was tested by evaluating the association between the K-BRIAN and the Morningness-Eveningness Questionnaire (MEQ). Results The mean K-BRIAN scores of the control subjects and patients with BD differed significantly (p<0.001). Particularly, the mean K-BRIAN score was considerably lower among control subjects (mean±standard deviation=35.00±8.88) than among patients with BD type I (41.19±12.10) and type II (50.18±13.73). The Cronbach’s alpha for the K-BRIAN was 0.914. The K-BRIAN was found to correlate with the MEQ (r=-0.45, p<0.001). Conclusion The findings affirm that the K-BRIAN has good construct validity and internal consistency. This suggests that the K-BRIAN can be used to assess biological rhythms in the Korean population, especially for patients with mood disorder.