Down syndrome (DS) is a common genetic disorder among Saudi children, for which limited data is available on growth for those who undergo surgery for congenital heart disease (CHD). We assessed the magnitude of growth over time following surgery and the factors associated with growth change. Eighty-eight children with DS and CHD who underwent surgery between 2009 and 2017 at the tertiary children's hospital in Al-Qassim, Saudi Arabia, were eligible. Information on gender, height, and weight (at surgery, 6 and 12 months), age at surgery, and type of CHD were abstracted from the medical records. Repeated measure analysis of variance (ANOVA) was used for data analysis. The sample's mean age (SD) was 16.2 months (20.1); 47% were male. Height, weight, and body mass index (BMI) increased significantly at both follow-up points. There was a significant interaction between age at surgery, type of heart disease, and time for all three physical indices (p-values <0.001). The increase in height, weight, and BMI was significantly greater for children ≤8 months old with acyanotic CHD compared to children >8 months with cyanotic CHD. Overall, the gain in growth was greater for the children with DS who had had surgery at a younger age.