Despite many studies on the prevalence of breakfast eating, we know little about factors that determine breakfast eating patterns. Our aim was to find out to which extent breakfast eating frequency is influenced by genetic and environmental factors using twin and twin-family models in a population sample of 16-year-old twins (n = 5250) and their parents (n = 4663). In common effects sex-limitation models, additive genetic effects explained 41% (95% CI: 21-63%) of the variance in breakfast eating in girls and 66% (95% CI: 47-79%) in boys, and common environmental effects 45% (95% CI: 23-62%) in girls and 14% (95% CI: 5-29%) in boys. Of twin-family models, phenotypic assortment models fitted the data best. Heritability estimates increased somewhat (72%, 95% CI: 46-98% in girls and 63%, 95% CI: 38-89%) in boys. Common family environment remained substantial in both sexes. Cultural transmission was nonsignificant. The relative influence of genetic and family factors on adolescent breakfast eating frequency differs by sex and is generation-specific.