Nutritional status disorders are a worldwide problem. Approximately 5.9 million children under the age of five die each year, and 45% of these deaths are related to malnutrition. The aim of the study was to analyse the prevalence of underweight children aged between 6 and 7 years old, living in the Gdańsk, Poland, in the years 1994–2020. The anthropometric parameters of 67,842 children were analysed. BMI (Body Mass Index) value p p = 0.670). The occurrence of underweight indviduals in the studied group slightly increased in the years 1994–2020. We found a statistically significant increasing linear trend in the analysis of underweight children in our group (p p p = 0.603; OLAF p = 0.787). This points to the need to conduct regular screening systems for children and adolescents.