Abstract: The general goal of this study is to analyze whether children-with-siblings lag behind their only-children counterparts in terms of health, cognition, and non-cognitive outcomes. We draw on a dataset containing 25,871 observations constructed from 3 school-level surveys spanning 4 provinces in China. The analysis is able to compare children-with-siblings with only-children aged 9 to 14 years old in terms of 8 different health, cognitive, and non-cognitive indicators. We find that with the exception of the anemia rate, health outcomes of children-with-siblings are statistically indistinguishable from those of only-children. In terms of cognition, children-with-siblings performed better than only-children. Moreover, outcomes of children-with-siblings are statistically indistinguishable from those of only-children in terms of the non-cognitive outcomes provided by measures of anxiety. According to our results, the same general findings are true regardless of whether the difference between children with and without siblings is disaggregated by gender.