Research Findings: The current project examined the unique and interactive relations of child effortful control and teacher-child relationships to low-income preschoolers' socioemotional adjustment. One hundred and forty Head Start children (77 boys and 63 girls), their parents, lead teachers, and teacher assistants participated in this study. Parents provided information on child effortful control, whereas lead teachers provided information on their relationships with students. Teacher assistants provided information on children's socioemotional adjustment (emotional symptoms, peer problems, conduct problems, prosocial behaviors) in the preschool classroom. Both teacher-child closeness and conflict were significantly related to low-income preschoolers' socioemotional adjustment (i.e., emotional symptoms, peer problems, conduct problems, and prosocial behaviors) in expected directions. In addition, teacher-child conflict was significantly associated with emotional symptoms and peer problems among children with low effortful control; however, teacher-child conflict was not significantly associated with socioemotional difficulties among children with high effortful control. Teacher-child closeness, on the other hand, was associated with fewer socioemotional difficulties regardless of children's level of effortful control. Practice or Policy: Results are discussed in terms of (a) the utility of intervention efforts focusing on promoting positive teacher-child interactions and enhancing child self-regulatory abilities and (b) the implications for children's socioemotional adjustment. (Contains 3 tables and 2 figures.)