Objective : Morus alba Linne Root Bark (MRAL) is a medicinal herb in Korean Medicine, known for its anti-inflammatory and anti-allergic properties. However, its mechanisms of action and the cellular targets have not yet been found and the study was developed to investigate the allergic suppressive effect of MRAL. The purpose of this study is to investigate the allergic suppressive effects of MRAL on activation of MC/9 mast cells. Methods : Cytotoxic activity of MRAL (50, 100, 200, 400 ${mu}g/mL$) on MC/9 mast cells measured using EZ-Cytox cell viability assay kit (WST reagent). The levels of interleukin-5 (IL-5), IL-13 and IL-4, IL-5, IL-6, IL-13 mRNA expression were measured by enzyme-linked immunosorbent assay (ELISA) and real-time PCR respectively. The expression of transcription factors such as GATA-1, GATA-2, NFAT, AP-1 and NF-${kappa}B$ p65 DNA binding activity were measured by western blot and electrophoresis mobility shift assay (EMSA). Results : Our results indicated that MRAL (50 ${mu}g/mL$, 100 ${mu}g/mL$) significantly inhibited PMA/Ionomycin-induced production of IL-5 and IL-13 and the expression of IL-4, IL-5, IL-6 and IL-13 mRNA in MC/9 mast cells. Moreover, MRAL (50 ${mu}g/mL$, 100 ${mu}g/mL$) inhibited PMA/Ionomycin-induced GATA-1, GATA-2, NFAT-1, NFAT-2, c-Fos protein expression and NF-${kappa}B$ p65 DNA binding activity in MC/9 mast cells. Conclusions : In conclusion, we suspect the anti-allergenic activities of MRAL, may be related to the regulation of transcription factors GATA-1, GATA-2, NFAT-1, NFAT-2, c-Fos and NF-${kappa}B$ p65 DNA binding assay causing inhibition of Th2 cytokines IL-5 and IL-13 in mast cells.