Mast cells are known to play a pivotal role in allergic diseases. Cross-linking of the high-affinity IgE receptor (FcεRI) is known to be one of the major causes that lead to degranulation and allergic inflammation. An increase in intracellular calcium (Ca(2+)) concentration also triggers degranulation, bypassing receptor activation. Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is known to exhibit a variety of pharmacological activities including anti-allergic effects. However, the detailed molecular mechanisms involved in exhibiting anti-allergic effects by emodin were remained to be clarified. In the present investigation we report the regulatory function of emodin on the allergic signal mediators through Ca(2+) ionophore activation in mast cells. Emodin significantly inhibited A23187-induced tumor necrosis factor-α production and degranulation through the attenuation of protein kinase C, IκB kinase 2, and soluble N-ethylmaleimide-sensitive fusion factor attachment protein receptor complex formation, bypassing FcεRI activation. Data from our study indicated that emodin acts by regulating multiple signaling pathways in inhibiting the allergic reactions in mast cells.