AimThe aim of our study was to develop a Tunisian risk score for pediatric hospital undernutrition. Patients and methodsWe conducted a prospective study, including all children aged over 30 days hospitalized for more than 48hours in pediatric department, over a six-month period. Hospital undernutrition was defined as a decrease of at least 25% in z-score of weight-for-height or BMI compared to admission. We developed a risk score for pediatric hospital undernutrition. ResultsWe followed 294 children with mean age of 43.6 months. The prevalence of undernutrition at admission was 25.5%. This prevalence increased at the end of the stay to 34%. The prevalence of hospital undernutrition was 28.6%. The risk factors for hospital undernutrition were: age ≤ 15 months (p=0.007), chronic disease (p=0.011), no breastfeeding (p=0.048), presence of fever on admission (p=0.040), food intake < 50% (p=0.008), and mother–child separation (p=0.029). A score of six items ranging from 0 to 20 was developed by assigning each risk factor its standardized coefficient. The threshold value was 4. This score was reliable (Cronbach's α = 0.9) and had a specificity of 80% and a sensitivity of 83%. ConclusionOur score had good psychometric properties and must be validated prospectively.