Protein–energy malnutrition (PEM) remains one of the common causes of morbidity and mortality among children throughout the world. The supplementation of 10 mg elemental zinc, as zinc sulphate, was evaluated in the management of PEM in a randomized, controlled double‐blind clinical trial in 300 children, aged 6–60 months (zinc, n = 150; control, n = 150) admitted to the Queen Elizabeth II Hospital, Maseru, Lesotho. Supplementation and follow‐up were done for 3 months post‐discharge from the hospital. Mortality during hospitalization was significantly lower in the zinc supplemented group (4.7 per cent), compared with 16.7 per cent in the control group. The prevalence of morbidity was significantly higher in the control group at 1, 2, and 3 month's follow‐up. In the zinc supplemented group 58 per cent of the children were above the 80th percentile of expected weight‐for‐age 3 months after discharge, compared with 27.6 per cent in the control group. Dietary zinc supplementation resulted in a significant reduction in diarrhoeal disease, respiratory morbidity, and episodes of clinical anaemia, skin infections, and fever as well as vomiting in children with PEM. These findings suggest that interventions to improve zinc intake in their management may be of benefit to Basotho children in Lesotho with PEM.