Background. Soil Transmitted Helminth (STH) infections are a major public health problem that affects more than two billion people around the world. These infections are the cause of children’s under nutrition, especially among school-aged children.

Objectives. To assess the correlation between the presence of STH infections and nutritional status among elementary school children in Medan, Indonesia.

Material and methods. We conducted an analytical cross-sectional study involving students from the public elementary school 060925 Medan in September 2015. The study participants were chosen by the total sampling technique and according to predetermined inclusion criteria (80 students from third and fourth grades). Univariate analysis was performed to determine STH infection prevalence, and bivariate analysis was used to find the correlation between STH infections and eosinophil levels through the chi-square (χ2) test.

Results. We found that the prevalence of STH among study subjects was 40%, and 26 students (32.5%) were underweight. The most common types of worm infections were Ascaris lumbricoides (25.0%), Trichuris trichiura (11.2%) and mixed infections (3.8%). A significant correlation was found between the presence of STH infection and underweight nutritional status (C = 0.24; χ2 = 5.02; p = 0.025) and the risk of STH infection and nutritional status in children with a prevalence ratio (PR) of 2.05 (CI 95%: 1.08–3.87).

Conclusions. The presence of STH infection in children is strongly influenced by their hygiene practices. Small clinics and student healthcare units should play an active role in conducting periodic assessment of children’s nutritional status and in providing them with information on STH symptoms and prevention.