Objective: To examine the prevalence of behavior disorders in a 2001–2003 birth cohort of extremely preterm/extremely low birth weight (EPT/ELBW, <28 weeks gestational age or <1000 g) children in kindergarten. Method: We compared 148 EPT/ELBW children with 111 term-born normal birth weight classmate controls on reports of psychiatric symptoms obtained from parent interview (Children's Interview for Psychiatric Syndromes-Parent Form [P-ChIPS]), parent and teacher ratings of behavior (Child Behavior Checklist, Teacher's Report Form, and Behavior Rating Inventory of Executive Function), and teacher ratings of social functioning (School Social Behavior Scales, second edition). Associations of behavior disorders with global cognitive ability and tests of executive function were also examined within the EPT/ELBW group. Results: Rates of attention-deficit/hyperactivity disorder combined on psychiatric interview were about twice as high for the EPT/ELBW group than for the normal birth weight group, odds ratio (95% confidence interval) = 2.50 (1.34, 4.68), p = .004. The EPT/ELBW group also had much higher rates of teacher-identified disorders in attention, behavior self-regulation, and social functioning, with odds ratios (95% confidence intervals) ranging from 3.35 (1.64, 6.83) to 18.03 (4.12, 78.94), all p values <.01. Attention-deficit/hyperactivity disorder and impaired behavior self-regulation were associated with deficits on tests of executive function but not with global cognitive impairment. Conclusions: The findings document increased rates of disorders in attention, behavior self-regulation, and socialization in EPT/ELBW children and suggest that deficits on tests of executive function are associated with some of these disorders. Early identification and intervention for these disorders are needed to promote early adjustment to school and facilitate learning progress.