Background: Evidence is emerging that early onset bipolar disorder and the duration of the delay to first treatment are both risk factors for poor treatment outcome. We report on the incidence and implications of these two risk factors in patients from the United States (US) versus Europe. Methods: Age of onset and age at first treatment for depression or mania was assessed in 967 outpatients with bipolar disorder who gave informed consent for participation and filling out a detailed questionnaire. Age at onset and treatment delay were compared in the 675 patients from the US and 292 from the Netherlands and Germany (abbreviated as Europe). Both were then graphed and analyzed. Results: Age of onset of bipolar disorder was earlier in the US than in Europeans by an average of 6–7 years with similar results in those with first onsets of depression or of mania. Delay to first treatment was strongly inversely related to age of onset and was twice as long in the US than in Europe, and especially different for mania in adolescents. The longer delay to treatment in the US was not solely due to earlier age of onset. Conclusions: Treatment delay is a remedial risk factor and could be shortened with better recognition of the higher incidence of early onset bipolar disorder in the US, which also associated with more genetic and environmental vulnerability factors compared to Europe. New treatment and research initiatives are needed to address these liabilities so that children with bipolar achieve more positive long-term outcomes.