Atopic dermatitis (AD) is a chronic inflammatory skin disease. K6PC-9 (N-Ethanol-2-hexyl-3-oxo-decanamide) is a novel synthetic ceramide derivative of PC-9S (N-Ethanol-2-mirystyl-3-oxo-stearamide), which was known to be effective in atopic and psoriatic patients. To investigate the immunomodulatory activity of K6PC-9, we examined the effect of K6PC-9 on T lymphocyte and macrophage function and the effect of topical application of K6PC-9 on skin inflammation and AD-like skin lesions in mouse models. K6PC-9 had no effect on concanavalin A-induced proliferation, interleukin (IL)-2 secretion and IL-4 secretion in mouse splenocytes. In contrast, lipopolysaccharide-induced nitrite generation was potently suppressed by K6PC-9 in mouse peritoneal macrophages. In mouse model of skin inflammation, K6PC-9 inhibited phorbol ester-induced increase in ear thickness and expression of tumor necrosis factor-alpha in the ear of BALB/c mice. Topical application of K6PC-9 also suppressed mite extract-induced AD-like skin lesions in NC/Nga mice. Increase in ear thickness was significantly inhibited by K6PC-9 in this model. K6PC-9 also blocked the infiltration of mast cells and neutrophils into the ear. Further study demonstrated that the mRNA expression of tumor necrosis factor-alpha and adhesion molecules, such as vascular cell adhesion molecule-1, intercellular adhesion molecule-1, E-selectin, was also suppressed by K6PC-9 in the ear of mite extract-treated NC/Nga mice. Taken together, the results presented in this report show that K6PC-9 has an anti-inflammatory potential and exerts beneficial effects in an animal model of AD, indicating that K6PC-9 might be used as a topical agent for the treatment of AD.