Poor drug compliance caused by side effects is an important factor affecting clinical outcomes. Thus reliable and valid rating scales to accurately evaluate the side effects of medications in their early stages are needed. This study aimed to develop the Korean version of the Udvalg for Kliniske Undersøgelser (UKU) Side Effects Rating Scale for Patients (K-UKU-SERS-Pat) to comprehensively measure side effects of psychotropic medications by the self-report method and to examine reliability and validity in patients with bipolar disorder (BD). Ninety-three patients diagnosed with BD by DSM-IV criteria were recruited in this study. The patients completed the K-UKU-SERS-Pat. The Side Effects Rating Scale for Clinicians was administered simultaneously. In 19 patients, the K-UKU-SERS-Pat was conducted twice on a 3-day interval to examine the test-retest reliability. Depressive symptoms were evaluated with the Hamilton Depression Rating Scale-17 and (hypo)manic symptoms with the Young Mania Rating Scale. The test-retest reliability (rho=0.89, P<0.01) and the concurrent validity (rho=0.80, P<0.01) of K-UKU-SERS-Pat were good. However, patients had a tendency to report their side effects more frequently and severely than clinicians. The K-UKU-SERS-Pat is proved to be a reliable and valid tool to comprehensively and practically monitor the side effects of psychotropics.