The present study investigated whether the complementarity principle (mutual interactive behaviors are opposite on control and similar on affiliation) applies to teacher-child interactions within the kindergarten classroom. Furthermore, it was examined whether interactive behaviors and complementarity depended on children's externalizing and internalizing behaviors, interaction time, and interaction frequency. A total of 48 teachers and 179 selected kindergartners with a variety of externalizing and internalizing behaviors were observed in a small group task setting in the natural ecology of the classroom. Teachers' and children's interactive behaviors were rated by independent observers. Teachers reported about children's externalizing and internalizing behaviors. Multilevel analyses indicated that both teachers and children reacted complementarily on the control dimension but not on the affiliation dimension. Teachers showed more control and more affiliation toward children with higher levels of internalizing behavior. In addition, teachers displayed less affiliation toward children with higher levels of externalizing behavior, whereas those children did not show less affiliation themselves. Teachers' and children's complementarity tendencies on control were weaker if children had higher levels of externalizing behavior. © 2012 Society for the Study of School Psychology.