Behavioral inhibition indicates increased risk for development of social anxiety. Recent work has identified a pattern of dysregulated fear (DF), characterized by high fear in low‐threat situations, that provides a more precise marker of developmental risk through early childhood. This study tested a new longitudinal sample of children (n = 124) from ages 24 to 48 months. Replicating prior findings, at 24 months, we identified a pattern of fearful behavior across contexts marked by higher fear to putatively low‐threat situations. DF was associated with higher parental report of social inhibition at 24, 36, and 48 months. Extending prior findings, we observed differences in cardiac physiology during fear‐eliciting situations, suggesting that the neurobiological underpinnings of DF relate to difficulty with regulation.