To examine the reciprocal relations between teacher-child relationships and children's behavior problems, the authors analyzed cross-lagged longitudinal data on teacher-child relationships and children's internalizing and externalizing problems using a structural equation modeling approach. The homeroom teachers of 105 first-year preschoolers aged 2-3 years filled in the Student-Teacher Relationship Scale and the Child Behavior Checklist/2-3, first at 3 months after the children's preschool entrance and then at the end of the first preschool year. Results showed significant cross-wave reciprocal relations between externalizing problems and teacher-child conflict and significant cross-wave relation from early internalizing problems to later teacher-child conflict. However, the cross-wave associations between internalizing and externalizing problems and teacher-child closeness were not significant.