Objective: The presence and specificity of a bipolar prodrome remains questioned. We aimed to characterize the prodrome prior to a first psychotic and nonpsychotic mania and to examine the phenotypic proximity to the schizophrenia prodrome. Methods: Using a semi-structured interview, the Bipolar Prodrome Symptom Scale-Retrospective, information regarding the mania prodrome was collected from youth with a research diagnosis of bipolar I disorder and onset before 19 years of age, and/or their caregivers. Only newly emerging, at least moderately severe, symptoms were analyzed. Prodromal characteristics were compared between patients with and without subsequent psychotic mania and with published bipolar and schizophrenia prodrome data. Results: In 52 youth (age at first mania: 13.4 ± 3.3 years), the prodrome onset was predominantly "insidious" (>1 year, 51.9%) or "subacute" (1–12 months, 44.2%), while "acute" presentations (