Background: Chinese chestnuts (C. mollissima Blume fruit) are valuable nutritional resources grown worldwide, having multiple health-promoting benefits and promising nutraceutical applications due to its enriched phytochemical contents and functional ingredients. In this study, fractions of different polarities were prepared from the Chinese chestnut to investigate their antioxidant, anti-inflammatory and phytochemical content.Methods: The total ethanol extract (TEE, 55g) of the peeled chestnut fruit was prepared by maceration with 80% ethanol, 10 g of TEE were further fractionated with dichloromethane to produce non polar fraction (NPF, 0.65 g) and polar fraction (PF, 9.3 g). TEE, PF and NPF were screened for their in vitro antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide ( NO) scavenging assays, the most active of which (TEE) proceeded to screen its anti-inflammatory activity by inhibition of cyclooxygenase enzymes (COX-1 and COX-2). The chemical composition of TEE and NPF was studied by UPLC/HR-MS/MS and GC/MS analyses respectively. Results: TEE showed the most potent DPPH and NO scavenging activity with IC50 (µg/mL) = 120.69± 0.54, and 230.02± 0.321, respectively, compared to vitamin C (213.5± 0.121 and 211.56 ± 0.181 µg/mL, respectively). TEE of C. mollissima showed selective anti-inflammatory effect against COX-2 not COX-1,with IC50 (µg/mL) 1.867 ± 0.115 and 38.25±0.68, respectively compared to indomethacin (0.13 ± 0.1; 27.031± 0.006 µg/mL) and celecoxib (4.18 ± 0.1; 92.52 ± 0.01 µg/mL) as reference drugs. UPLC-MS/MS analysis of TEE tentatively identified 41 metabolites that included 4 organic acids, 12 flavonoids, 4 phenolic compounds, 5 polyphenol, 9 fatty acids, 2 phospholipids and 1 triterpene, several of which are described for the first time in Chinese chestnut. GC/MS analysis of the non-polar fraction (NPF) revealed 32 unsaponifiable compounds (75.19%) including 25.98%, oxygenated, 20.92% oxygenated nitrogenous. and 28.29% non-oxygenated compounds in addition to 17 fatty acids as methyl esters (96.30%) that included 32.22% unsaturated and 64.08%. saturated fatty acids. Conclusion: The in vitro bioactivity study suggested that total ethanol extract had a synergistic effect among its constituents that was relatively alleviated upon fractionation into polar and non-polar fractions. Chinese chestnut is an enriched resource of diverse phytochemicals having great nutraceutical potential.