We analyze the relationship between birth order, parental health investment and children’s health using administrative data from Austria. We show that later-born children have better health endowments at birth. They are less likely born preterm or with a low birth weight, and less likely hospitalized for perinatal conditions. We also find significant birth order differences in parental health investment in early childhood. Later-born children are less likely to participate in preventive medical screenings and their vaccine uptake rates are lower. Our analysis indicates that these birth order differences in parental health investments are not driven by children’s health endowments. Thus, we do not find evidence for compensatory behavior of parents. We discuss alternative explanations, such as the role of resource constraints. Furthermore, we show, that the initial health inequalities extend into middle childhood. Later-born children show a better health status in school health checks, they consume less medication and are less often hospitalized.