Data from 508 Caucasian children in the NICHD Study of Early Child Care and Youth Development shows that the DRD4 (but not 5‐HTTLPR) polymorphism moderates the effect of child‐care quality (but not quantity or type) on caregiver‐reported externalizing problems at 54 months and in kindergarten and teacher‐reported social skills at kindergarten and first grade—but not thereafter. Only children carrying the 7‐repeat allele proved susceptible to quality‐of‐care effects. The behavior–problem interactions proved more consistent with diathesis‐stress than differential‐susceptibility thinking, whereas the reverse was true of the social‐skills' results. Finally, the discerned Gene × Environment interactions did not account for previously reported parallel ones involving difficult temperament in infancy.