The influence of the epistemological beliefs of parents on the development of comprehensive scientific reasoning abilities was investigated in a five-wave longitudinal study from kindergarten to elementary school. The 161 German 5-10-year-olds (89 girls, 72 boys) were assessed yearly on their scientific reasoning abilities using comprehensive measures for experimentation and data-interpretation skills, as well as understanding of the nature of science. The children were also tested on their language abilities and intelligence. Their parents completed a sociodemographics questionnaire and answered ten questions about their epistemological beliefs regarding (1) the interpretive nature of science, (2) the tentative nature of knowledge, and (3) the role of scientific framework theories. The personal epistemology of the parents significantly predicted the scientific reasoning development of their children regardless of the parents' education level and the children's general cognitive abilities. However, the effect of the epistemology of parents on their children's scientific reasoning was limited to the intercepts, suggesting that the epistemic understanding of parents affects how scientific reasoning develops in their children, but not the development speed. Although parental epistemology exerts substantial effects on scientific reasoning of their children, it did not affect their reading ability, suggesting an involvement of science-specific mechanisms rather than generalized family-based influences. These findings highlight the importance of family as a variable in the development of scientific reasoning, which is an area lacking in research, and it suggests that early interventions targeted at the epistemic understanding of caregivers can provide useful ways for promoting the reasoning of children.