Objective: Clinical rating scales are essential in psychiatry. The Young Mania Rating Scale is the gold standard for assessing mania. However, increased attention to pediatric bipolar disorder has led to the development of the Child Mania Rating Scale (CMRS), which is a parent-reported rating scale designed to assess mania in children and adolescents. This study aimed to translate the CMRS into Korean and assess the validity and reliability of the Korean version of the CMRS (K-CMRS). Methods: The original English version of the CMRS has been translated into Korean. We enrolled 33 patients with bipolar disorder and 26 patients with attention-deficit hyperactivity disorder (ADHD). All participants were evaluated using the translated K-CMRS, Mood Disorder Questionnaire (MDQ), and ADHD Rating Scale. Results: The Cronbach’s α was 0.907. Correlation analyses between K-CMRS and MDQ scores yielded significant positive correlations (r=0.529, p=0.009). However, the factor analysis was unsuccessful. The total K-CMRS scores of bipolar disorder and ADHD patients were compared. However, the differences were not statistically significant. Conclusion The K-CMRS showed good internal consistency and reliability. The correlation between the K-CMRS and MDQ scores verifies its validity. The K-CMRS was designed to assess and score manic symptoms in children and adolescents but had difficulties in differentiating between bipolar disorder and ADHD. It is a valuable tool for evaluating the presence and severity of manic symptoms in pediatric patients with bipolar disorder.