Although psychometrically-defined executive function deficits (EFDs) and ecologically valid functional outcomes have been documented among youth with bipolar I (BP-I) disorder, little is known about their association. We hypothesized that EFDs would be associated with significant ecologically valid impairments beyond those predicted by having BP-I disorder. Youth with BP-I disorder were ascertained from psychiatric clinics and community sources. We defined EFDs as having at least two out of eight EF measures impaired from a battery of six tests. Significantly more youth with BP-I disorder had EFDs than controls (45% versus 17%). Comparisons were made between controls without EFDs (N=81), controls with EFDs (N=17), BP-I youth without EFDs (N=76), and BP-I youth with EFDs (N=62). EFDs were associated with an increased risk for placement in a special class and a decrease in academic achievement (WRAT-3 reading and arithmetic). EFDs in BP-I subjects were associated with an increased risk for speech/language disorder (as assessed in the K-SADS-E) relative to BP-I subjects without EFDs. Youth with BP-I disorder and EFDs are at high risk for significant impairments in academic functioning.