In this study, we investigated the anti-inflammatory and anti-allergic effects of Stichopus japonicus extract. The anti-inflammatory effect of S. japonicus was evaluated using the Griess reaction to evaluate nitric oxide (NO) release and reverse transcriptase-PCR (RT-PCR) to determine interleukin (IL)-6 and tumor necrosis factor-${alpha}$ (TNF-${alpha}$) mRNA expression levels in LPS-stimulated RAW 264.7 murine macrophages. The anti-allergic activity of S. japonicus was investigated by performing ${eta}$-hexosaminidase assay on antigen-stimulated RBL-2H3 rat mast cell lines and IL-4 mRNA expression. Our data revealed that S. japonicas water fraction (SJW) inhibited NO release without cytotoxicity in LPS-stimulated Raw 264.7 cells. The levels of IL-6 and TNF-${alpha}$ mRNA reduced following SJW treatment. In addition, SJW inhibited antigen-induced degranulation (e.g., $IC_{50}$ value of $658{mu}g/mL$) as well as IL-4 mRNA expression. Our results suggest that SJW possesses anti-inflammatory and anti-allergic effects.