Interferon-alpha (IFN-α) is used for the treatment of chronic viral hepatitis. However, it has been associated with adverse psychiatric side effects. These IFN-α-associated psychiatric symptoms include depression (most frequently), personality change, and impaired cognition; sometimes psychosis and delirium; and rarely mania and suicidal tendencies. Most of these side effects disappear rapidly after the cessation of IFN-α treatment. Here, we report a rare case of chronic hepatitis B in which psychotic mania developed during the resumption of IFN-α treatment. The manic episode persisted for two months and required inpatient psychiatric management, despite the discontinuation of IFN-α and administration of antimanic treatments. To our knowledge, this is the first case of bipolar disorder induced by resuming IFN-α in the treatment of chronic hepatitis B. This case indicates the importance of careful monitoring and treatment of psychiatric side effects in patients receiving IFN- α therapy for chronic viral hepatitis.