Using data from the baseline wave of the China Family Panel Studies, we applied three-level random-intercept logistic regression models to investigate how the child gender gap in intergenerational support differed between one- and multi-child families in China based on 16,201 parent–child dyads. The results showed that sons were more likely to receive both financial and instrumental support from elderly parents. Additionally, sons tended to provide financial support and daughters tended to provide instrumental support. Being in a one-child family increased the chance of children’s receipt of support, but not support provision from/to elderly parents. A difference in child gender gap was only found for children’s receipt of instrumental support, which was less in one-child families than in multi-child families. The findings suggest that the gendered pattern of intergenerational support has not changed in one-child families, which has implications for the provision of services for elderly care, considering families with different structures.