Si-Ni-San (SNS) is a well-known decoction in traditional Chinese medicine. Although studies have indicated that the anti-inflammatory and anti-allergic properties of SNS and its components can account for their therapeutic effects, the role and mechanism of SNS in treating skin dysfunction remain unclear. Atopic dermatitis (AD), a disorder known for its prevalence in infants and adults, severely influences the quality of life of affected patients. In this study, we aimed to investigate the anti-inflammatory and immune response modulations of SNS in 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin dysfunction. Dermatitis was induced in Kunming mice by the topical application of DNCB. SNS or dexamethasone (positive control) was topically applied every day over the course of the 21-day study. The following were assessed: dermatitis severity scores; ear and dorsal skin haematoxylin and eosin staining; interleukin (IL)- 1α, IL-1β, IL-2, IL-4, IL-6, and tumour necrosis factor (TNF)-α cytokine levels in the serum; spleen index; spleen CD4 + /CD8 + T lymphocyte ratio; and phosphorylation levels of mitogen-activated protein kinases (MAPKs- p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK)), IκB-α, and nuclear factor (NF)-κB (p65) in skin lesions. SNS significantly alleviated the symptoms of AD-like lesions induced by DNCB, decreased the infiltration of inflammatory cells in the ear and dorsal tissues, suppressed the increased cytokine levels in the serum, reduced the CD4 + /CD8 +T lymphocyte ratio in the spleen, and downregulated the activation of MAPKs, IκB-α, and NF-κB (p65) in the dorsal skin. The effects were similar to those of dexamethasone. SNS alleviated the DNCB-induced AD-like skin dysfunction in mice through anti-inflammatory and immune system modulation, indicating that SNS shows potential for AD treatment in clinical settings. Copyright © 2018 Elsevier B.V. All rights reserved.