Previous research on antecedents of generalized control expectancies has indicated that parents of children with internal control expectancies express more warmth than parents of children with external control expectancies. However, few studies have utilized observational methodologies and no study has identified a specific mechanism by which parental warmth may contribute to differences in children's control expectancies. In addition, no study has examined whether individual differences in children's behavior are associated with differences in parental warmth. We tested the hypothesis that mothers of internally and externally controlled children would differ in their expression of nonverbal behavioral indicators of warmth. To test the hypothesis, the interactions of 50 second-grade children and their mothers were videotaped. Compared to mothers of externally controlled children, mothers of internally controlled children displayed more smiles, exhibited more positive touches (hugs, pats, rubs), and gazed for longer periods of time toward their child. Analyses of the children's behavior revealed that internally controlled children displayed more smiles and engaged in less off-task behavior than externally controlled children. Results of the current study further clarify the nature of the association between parental warmth and children's generalized control expectancies and suggest nonverbal behavior as a possible mechanism.