Background: Amesiodendron chinense (Merr.) Hu (family: Sapindaceae) is a Thai medicinal plant. The seed oil of this species has been used by folk healers and local people in southern Thailand for the treatment of wounds, skin disorders and common hair problems. This study aimed at the GC-MS-based determination of the chemical composition of the seed oil of this plant, and evaluation of its Nrf2/ARE induction activity in AREc32 cells (modified human breast cancer cell line MCF-7) using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and luciferase reporter gene assays. Results: GC-MS analysis identified 9-(E)-octadecenoic acid (84.82%) as the main component of this seed oil. TLC-based qualitative DPPH (2,2-diphenyl-1-picrylhydrazyl) assay revealed the DPPH radical-scavenging activity of the seed oil and its chromatographic fractions. A low-level DPPH-scavenging activity was observed in the quantitative assay, but no IC50 value could be determined even with the highest tested concentration (10 mg/mL). Neither the oil nor its chromatographic fractions showed any significant Nrf2/ARE induction in AREc32 cells. The seed oil was noncytotoxic against the AREc32 cells. Conclusions: A. chinense seed oil and its fractions had a low level of free-radical scavenging property but no significant Nrf2/ARE induction activity in AREc32 cells. However, as the oil did not show any cytotoxicity at test concentrations in the MTT assay, this oil might potentially be safe to use in cosmetic formulations or as a vehicle for the dermal delivery of drug molecules.