Individual differences in personality play a major role for functioning in a multitude of important life domains, including one's interpersonal relationships. The present study examined the effects of parental personality and child temperament traits on dyadic parent-child interaction during early childhood. Participants were a community sample of 145 mothers, 145 fathers, and their 3- to 6-year-old children. Child traits were assessed using standardized laboratory paradigms, parents reported on their own traits, and parent-child interaction was assessed observationally. Parental positive emotionality, negative emotionality, and constraint subtraits were related to parental responsiveness; the number and type of parental bids and the quality of parental responsiveness were also a function of child positive emotionality and effortful control subtraits and, for mothers, child negative emotionality subtraits. Child traits were related to their own interaction behaviors; children higher on positive emotionality subtraits made more social bids, and children higher on effortful control subtraits made more influence attempts and fewer negative bids; child positive emotionality and effortful control subtraits were associated with higher quality child responsiveness. Findings speak to coherence in personality constructs across the life span, with comparable traits measured in adults and early childhood–aged children demonstrating remarkably consistent effects on dyadic interaction behavior.