Effective regulatory skills are essential in busy preschool classroom environments where children must maintain some control over their emotions and behavior to interact effectively with peers and teachers. Regulatory abilities can play a crucial role in a child's successful adjustment to preschool. We investigated whether individual differences in dysregulation (emotional and behavioral) as observed in the naturalistic classroom context were associated with peer social competence and teacher ratings of classroom adjustment in a sample of low-income preschoolers. Naturalistic observational methods were used to assess dysregulated emotions and behaviors in Head Start classrooms. Findings demonstrate that although displays of observed dysregulation were relatively brief, about one-quarter of children showed high levels of dysregulation, and individual differences in dysregulated behavior predicted teacher-rated classroom adjustment and peer conflict. Research results are discussed with regard to implications for classroom practice and prevention.