A growing body of research suggests that bipolar spectrum disorders (BSDs) are associated with high aggression. However, little research has prospectively examined how aggression may affect time to onset of hypomanic/manic versus major depressive episodes. In a longitudinal study, we tested the hypothesis that aggression would prospectively predict a shorter time to the onset of hypomanic/manic episodes and a longer time to the onset of major depressive episodes, based on the behavioral approach system theory of BSDs. Young adults (N=120) diagnosed with cyclothymia, bipolar II disorder, or bipolar disorder not otherwise specified were followed every 4 months for an average of 3.55 years. Participants completed measures of depressive and manic symptoms, family history of mood disorder, impulsivity, and aggression at baseline and were followed prospectively with semistructured diagnostic interview assessments of hypomanic/manic and major depressive episodes and treatment seeking for mood problems. Cox proportional hazard regression analyses indicated that overall, physical, and verbal aggression predicted a longer time to major depressive episode onset, even after controlling for baseline depressive and manic symptoms, family history of mood disorder, treatment seeking for mood problems, and impulsivity. Aggression, however, did not significantly predict time to onset of hypomanic/manic episodes, controlling for the same covariates. The findings suggest that approach-related behaviors may be utilized to delay the onset of major depressive episodes among people with BSDs.