Background Zinc supplementation has varied effects on the linear growth of children who exhibited stunted growth. Materials and Methods This observational study involved 761 undernourished children, aged 2–10 years, who received a 24‐week course of 10‐mg elemental zinc per day. The clinical parameters for evaluation included appetite, height, weight, and body mass index (BMI). Evaluation of the effect of zinc supplementation was stratified by the initial serum zinc concentration. Results The enrolled participants comprised 390 boys and 371 girls. The mean age was 5.63 years. The height‐for‐age, weight‐for‐age, and BMI‐for‐age z scores increased gradually during the study period. When compared with the children with a serum zinc concentration ≥75 μg/dL, the height, weight, weight‐for‐age, and BMI‐for‐age z scores increased significantly in the patients with serum zinc concentrations of <75 μg/dL after 12‐ and 24‐week zinc supplementation (all P < .001). BMI, height‐for‐age z score, and appetite also increased significantly in patients with serum zinc concentrations of <75 μg/dL after 24‐week zinc supplementation (P = .003, .019, and <.001, respectively). Conclusion The findings of this study indicate that undernourished children with serum zinc concentrations of <75 μg/dL experienced greater increments in appetite and growth as a result of zinc supplementation.