Knowledge of child development influences parental expectations of, and interactions with, children. Studies have shown that maternal knowledge supports cognitive and social–emotional development of young children and can have long-lasting benefits. Level of developmental knowledge of parents and grandparents has seldom been investigated on a population level. Our aim was to compare Canadian and Dutch samples of urban parents and grandparents in terms of normative knowledge of children’s cognitive and social–emotional development. Urban parents ( n = 379) and grandparents ( n = 174) from the province of Alberta, Canada ( N = 553) and parents ( n = 634) and grandparents ( n = 96) of the city of The Hague in the Netherlands ( N = 730) answered questions related to knowledge of cognitive and social–emotional development of young children, including topics such as “do children have stronger bonds with parents who stay at home instead of working outside the home?” and “do children learn more from hearing someone in the same room talk than hearing someone on TV?” Overall, the Canadian respondents were more likely to answer these questions correctly. In both samples, women were more likely than men to answer correctly. No significant relationship between age or role (parent or grandparent) and knowledge was identified, but there was a positive correlation between knowledge and level of education. Little is known about international differences in caregivers’ knowledge about normative child development. This study suggests that differences exist. Understanding differences between countries in parental knowledge may provide insight into cross-cultural variability in child behavioral and developmental outcomes.