Objective: This study evaluated the theory of mind (ToM) in adolescents diagnosed with bipolar disorder (BD) during their euthymic period compared to a typically developing (TD) group. Method: The BD group consisted of thirty 11-18 year old inpatients in euthymic phase. The TD group included 30 age, gender, and IQ matched volunteer students. To assess the diagnosis and comorbid disorders, we performed the semi-structured interview of the Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version (K-SADS-PL) for the BD adolescents. To evaluate the severity of attention deficit hyperactivity disorder (ADHD) and mania, Conner's Parent Rating Scale-Revised version (CPRS-R), and Young Mania Rating Scale (YMRS) were used, respectively. Ravens Progressive Matrices was conducted to evaluate intellectual ability in the both groups. Happe Strange Stories test was performed to assess ToM in the participants. Data were analyzed using the independent t-test, analysis of covariance, and Pearson Correlation analysis. Results: The two groups did not show any differences in comprehending the stories; however, the BD group's mentalizing scores were significantly weaker than the TD group (p<0.05). Conclusion: The ToM impairments in adolescents with BD may be explained as a trait marker which may lead to continuation of social problems even during remission..