There is a dearth of research examining the relation between culture and childhood self-regulation in family psychology. Family orientation refers to the emphasis on providing support, respect, and obligation to the family system, and it is important for children's functioning, yet existing literature on related constructs often relies on parent-reported measures. Additionally, twin research has neglected the role of culture in the genetic and environmental contributions to children's self-regulation. Using observational and self-reported data from children, parents, and teachers, this study (a) proposed novel coding schemes and factor analytic approaches to capture family orientation, (b) examined associations between family orientation and selfregulation, and (c) tested whether family orientation moderated the heritability of self-regulation in middle childhood. Twin children (N = 710; M age = 8.38 years, SD = 0.66; 49.1% female; 28.3% Hispanic/Latino/x, 58.5% White) were drawn from the Arizona Twin Project, which recruited children from birth records at 12 months of age. Family orientation values were indexed by parent-reported familism, and family orientation behaviors comprised coded measures of children's family orientation and experimenter ratings of caregiver and child behavior. Self-regulation was assessed using multiple task-based assessments of executive function and parent-and teacher-reported effortful control. Net of covariates, higher family orientation behaviors positively predicted nearly all measures of children's self-regulation, and associations were consistent across sex, family socioeconomic status, and race/ethnicity. There was no evidence that family orientation values nor behaviors moderated the heritability of children's self-regulation. This study highlights the complex nature of cultural variation within the family and its importance for children's self-regulatory abilities.