Objective The aim of this study was to evaluate differences in psychopathology between offspring of parents with bipolar Ⅰ disorder (BP-Ⅰ) and those with bipolar Ⅱ disorder (BP-Ⅱ). Methods The sample included 201 offspring between 6 and 17 years of age who had at least one parent with BP-Ⅰ or BP-Ⅱ. The offspring were diagnostically evaluated using the Korean Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version. Psychopathology and Clinical characteristics were evaluated, including lifetime DSM-5 diagnoses, depression, and childhood trauma. Lifetime DSM-5 diagnoses were also compared between schoolchildren aged 6 to 11 years and adolescents aged 12 to 17 years. Results In lifetime DSM-5 diagnoses, offspring of parents with BP-Ⅰ had significantly increased risk of developing MDD and BP-Ⅰ than those with BP-Ⅱ. Regarding clinical characteristics, ADHD rating scale and childhood trauma scale were significantly higher in offspring of parents with BP-Ⅰ than that in those with BP-Ⅱ. Conclusion The present study supports that BP-Ⅰ may be etiologically distinct from BP-Ⅱ by a possible genetic liability. Our findings indicate that additional research related to bipolar offspring is needed to enhance understanding of differences between BP-Ⅰ and BP-Ⅱ.