Herbal medicine has a high body absorption rate when it ferments. Biological and clinical research on the fermented herb gradually increases because it has effective materials for the treatment of a disease and it is a little bitter. In this study, we investigated the effect of fermented Baedokhwanbalhyobang (BDHBH) on attenuation of the development of atopic dermatitis in NC/Nga mice by evaluating the cytokine level in serum, the mRNA expression of cytokine and histological alteration of the skin, and the skin severity. We have come to the following conclusion. BDHBH led to a significant decrease in the skin severity score (63.1%) as compared to the control group. CD4+/CD45+, CD4+, B220+/CD23+, and CD11b+/Gr-1+cells of peripheral mononuclear cells (PBMCs) in the BDHBH-treated group were decreased to 6.7%, 31.1%, 22.4%, 36.6%, respectively. CD3+and CD11b+/Gr-1+immune cells in dorsal skin of the BDHBH-treated group were decreased to 52.9% and 28.0%. The levels of IL-5 and IL-13 in serum of the BDHBH-treated group were inhibited to 18.8% and 5.1%. The mRNA expressions of IL-5 and IL-13 in dorsal skin were also decreased to 30.6% and 27.8% after the treatment of BDHBH. BDHBH inhibited the proliferation and differentiation of eosinophils. In histological examination, BDHBH decreased the thickness of epidermis and dermis, and infilatration of mast cells as compared to the control group. These results indicate that BDHBH inhibits the pathogenic development of atopic dermatitis in NC/Nga mice. These results may indicate that BDHBH attenuates the development of atopic dermatitis-like lesions by lowering immune cells and inflammatory cytokine levels, and that it is valuable in drug development for the treatment of atopic dermatitis. Further experiments on the components of BDHBH will be needed to better understand the effect of a fermented herb as compared to a herb.