Chamaecyparis obtusa (CO) has recently been attracting attention because of its beneficial effects on skin allergies, atopic dermatitis, and skin diseases, such as acne and eczema. In the present study, the extract from CO leaf grown in Jangseong gun, Jeollanam-do, Korea was evaluated for its anti-oxidant, anti-inflammatory, and anti-allergic effects in vitro. The total polyphenol content of the CO leaf extract was 25.89±0.31 mg gallic acid equivalents (GAE)/g. Gas-chromatography mass-spectrometry (GC-MS) analysis revealed the presence of six compounds in the CO leaf extract: α-terpinene (3.03 mg/g), α-terpineol (9.48 mg/g), limonene (5.96 mg/g), borneol (59.78 mg/g), myrcene (4.85 mg/g), and sabinene (11.31 mg/g). The RC50 values of the CO leaf extract for H2O2 and ABTS radical were 5.47±0.13 mg/mL and 4.00±0.01 mg/mL, respectively. In addition, the CO leaf extract showed significant inhibitory effects on lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells and IgE-induced release of β-hexosaminidase (degranulation) in mast-cell like RBL-2H3 cells. The cell viability assay showed that the CO leaf extract (100∼800 μg/mL) did not affect the viability of human normal skin fibroblast CCD-986sk cells significantly. Overall, these results suggest that the CO leaf extract is a potential functional cosmetic ingredient that can exert anti-oxidant, anti-inflammatory, and anti-allergic effects.