--- - |2 Abstract Elevated and persistent childhood unresponsiveness to others (not responding to cues from others during interactions) may be due to a combination of early environmental and biological influences. However, little is known about how sensitive parenting may influence minute‐to‐minute changes in child unresponsiveness. The present study examines trajectories of child unresponsiveness to parent and parent sensitivity across a 10‐minute parent–child interaction, and also examines variation by children's DRD4 genotype. Child unresponsiveness and parent sensitivity were assessed minute by minute for 246 twins during a puzzle task. Latent growth curve models demonstrated that increasing trajectories of child unresponsiveness and decreasing trajectories of parent sensitivity were associated across the 10‐minute interaction. When examined by genotype, this association was present only for children with the DRD4 7‐repeat allele (the putative ‘risk’ allele). In addition, initial levels of parent sensitivity predicted trajectories of child unresponsiveness only in children with a DRD4 7‐repeat allele. This examination of gene‐environment interaction illustrates the value of considering both genotype and the parenting environment in consideration of preschool children's development of unresponsive behavior. It also supports the importance of investigating the interplay between minute‐level parenting and child behavior in explaining child development. - Social Development, Volume 27, Issue 4, Page 952-966, November 2018.