Aims:  This study aimed to define the nutritional state of children admitted to a tertiary Iranian hospital and to evaluate nutritional risk score tools in these children.

Methods:  The anthropometry of hospitalized and healthy children from the same community was determined. Three nutritional risk score tools were applied to all inpatients.

Results:  One hundred and nineteen inpatients were recruited along with a comparison group of 100 children. The prevalence of under‐nutrition in the inpatient group was 25.2% and 3% in the community group (p < 0.0001). Obesity/overweight was more prevalent in the community group than the inpatients (22% versus 2.5%: p = 0.04). Severely malnourished children had a longer hospital stay than those with normal nutrition (p < 0.0001). The nutritional risk score tools identified between 83% and 90% of the malnourished patients in the moderate and high‐risk groups. The STRONG_kids tool correlated more strongly with anthropometric measurements than the other tools. The length of hospital stay was associated with risk status (p = 0.004).

Conclusion:  Hospitalized Iranian children have higher rates of under‐nutrition than healthy children from the same community. NRS tools were able to identify children at nutritional risk; however, variable utility was observed. Further assessment of NRS tools in the developing setting is required.