Background: Recent data suggested that imbalance in gut microbiota and gastrointestinal inflammation is associated with the childhood allergic diseases. Fecal calprotectin has been used for a non-invasive marker of gut inflammation. Objective: The aim of this study was to investigate the relationships between fecal calprotectin levels and the clinical severity of atopic dermatitis (AD) in children. Methods: We enrolled 65 subjects with AD. The concentration of calprotectin was measured in each subject’s fecal sample. Results: The geometric mean fecal calprotectin level of the total subjects was 33.1(10.1-108.9) μg/g. Among the 65 subjects, 44(67.7%) showed calprotectin levels lower than 50μg/g(Group 1), and 21(32.3%) were higher than 50μg/g(Group 2). The mean SCORAD index was significantly higher in Group 2 than Group 1(31.0±16.0 vs 22.2±15.3, p=0.046). The geometric mean serum total IgE levels was higher in Group 2 compared to Group 1(361.4[31.6-992.3]IU/mL vs 175.9[44.3-699.2]IU/mL, p=0.040). The mean blood eosinophils were significantly higher in Group 2 than in Group 1(497.7[239.8-1032.8]/μL vs 281.5[121.5-652.0]/μL, p=0.034). The incidence of exposure to environmental tobacco smoke was significantly higher in Group 2 compared to Group 1(76.2% vs 47.7%, p=0.036). Geometric mean fecal calprotectin level in severe AD was significantly higher than that of mild-to-moderate AD(66.7[13.5-330.3]μg/g vs 29.4[10.1-85.6]μg/g, p=0.044). The fecal calprotectin level significantly correlated with the SCORAD index(r=0.303, p=0.014). Conclusions: Higher fecal calprotectin levels were observed in subjects with severe AD. Elevated fecal calprotectin levels as a gastrointestinal inflammatory marker may associate with childhood AD. Measurement of fecal calprotectin might be useful for assessment of severity of childhood AD.