The antioxidant properties of oil and fruit extracts of Tetracarpidium conophorum (African walnut) from four weeks after anthesis(WAA) to fruit maturation were assessed in this study. The oils from the fruits were extracted with chloroform-methanol 1:2 (v/v), and the methanol extracts of the fruit seeds were also prepared using standard procedures. The in vitro antioxidant capacity of the fruits and oil extracts was determined by spectrophotometric methods using 2, 2-diphenyl-1- picrylhydrazyl (DPPH) radical, H2O2 and malondialdehyde (MDA) assays. Results from the study indicated that DPPH and H2O2 scavenging capacity as well as percentage inhibition of MDA were significantly (P˂0.05) higher inoil 20 WAA (48.34±0.12%,46.9±1.03%,53.5±0.46%)and whole fruit extracts at 20 WAA (31.84±0.33%, 19.0±1.12%, 51.7±0.26%) respectively,but with significant (P˂0.05) lesser percentage of inhibition at 4-12WAA in both the oil and the whole extracts. The hepatoprotective effects of the extracts were examined in vivo in male wistar rats challenged with sodium arsenate. Results showed that the rats fed with the oil and whole fruit extracts had significant reduction (p<0.05) in lipid peroxidation, increase in superoxide dismutase (SOD) and catalase (CAT) activities especially at 16-20 WAA relative to control values. African walnutextracts treated rats also showed similar decrease in serum AST (122.7±2.58U/L), ALT (59.1±2.49U/L), ALP (20.4±0.15U/L) and GGT (229.0±0.36U/L) levels at 20 WAA when compared to 4 WAA extracts treated rats, AST (129.3±0.64U/L), ALT (72.3±2.59U/L), ALP (34.4±0.08U/L) and GGT (299.7±1.27U/L). The results suggest that the various fruit extracts possess varied degrees of potent antioxidant activity both in vitro andin vivo and may serve as important sources of antioxidants in food, cosmetics and pharmaceutical industries.