The relationship between household size and future health outcomes for children is of immense interest to economists, demographers and policy-makers especially in developing countries. One reason for this is that child health is a key determinant of future human capital. This is particularly important in South Africa with high levels of unemployment, poverty and gross income inequality. Moreover, the quantity-quality model of fertility indicates a trade-off of children's welfare with increasing family size. However, despite the forgoing, relatively little empirical research has been done regarding this nexus, especially in developing countries. Furthermore, while the few studies have mainly relied on cross-sectional data, this study takes advantage of the availability of the recent National Income Dynamic Study (NIDS) panel data set to empirically assess this link. We make use of both the Generalized Method of Moments (GMM) and the Control Function (CF) approaches to account for econometric issues such as heterogeneity and endogeneity. These results suggest fertility choices has a significant association with child health. Moreover, younger children are more likely to be affected by increased household size. These results are concordant with theoretical expectations. From a policy perspective, these findings indicate that intensified child support is likely to improve child health outcomes in South Africa, particularly among the black racial group where fertility is comparatively higher. Moreover, family planning programs especially in the rural areas of the country, should be promoted. In addition, the empowerment of women through provision of funding for schooling and skills development could also contribute to better child health outcomes.