Objectives PRAL (Prunus armniaca Linne Var) is a herbal formula in Oriental Medicine, known for its anti-inflammatory and anti-allergenic properties. However, its mechanism of action and the cellular targets have not yet been found enough. The purpose of this study is to investigate the effects of PRAL on Th2 cytokines expression in MC/9 mast cells. Methods The effect of PRAL was analyzed by ELISA, Real-time PCR, Western blot in MC/9 mast cells. mRNA levels of GM-CSF, IL-4, IL-5, IL-6, IL-13, TNF-${alpha}$ were analyzed with Real-time PCR. Levels of IL-13, MIP-$1{alpha}$ were measured using enzyme-linked immunosorbent assays (ELISA). NFAT, AP-1 and NF-${kappa}B$ p65 were examined by Western blot analysis. Results PRAL inhibited GM-CSF, IL-4, IL-5, IL-6, IL-13, TNF-${alpha}$ mRNA expression in a dose dependent manner. GM-CSF, IL-4, IL-5 mRNA expression were inhibited significantly in comparison to DNP-IgE control group at concentration of 100 ${mu}g/ml$ and IL-6, IL-13, TNF-${alpha}$ mRNA expression were inhibited at concentration of 50 ${mu}g/ml$, 100 ${mu}g/ml$. PRAL also inhibited the IL-13, MIP-$1{alpha}$ production significantly in comparison to DNP-IgE control group in a dose dependent manner. IL-13 production was inhibited at a concentration of 200 ${mu}g/ml$, 400 ${mu}g/ml$ and MIP-$1{alpha}$ was inhibited at a concentration of 100 ${mu}g/ml$, 200 ${mu}g/ml$, 400 ${mu}g/ml$. Western blot analysis of transcription factors involving Th2 cytokines expression revealed prominent decrease of the mast cell specific transcription factors including NFAT-1, c-Jun as well as NF-${kappa}B$ p65 but not NFAT-2 and c-Fos. Conclusion These results indicate that PRAL has the effect of suppressing Th2 cytokines production in the MC/9 mast cells. These data represent that PRAL potentiates therapeutic activities to the allergic disease by regulating Th2 cytokines in the MC/9 mast cells.