To assess nickel-induced toxicity in plants, an experiment was performed focusing on the metabolic adaptation of Luffa cylindrica seedlings to nickel-induced oxidative stress. Luffa cylindrica (sponge gourd) seeds were germinated and cultured in the Murashige and Skoog (MS) media with nickel concentrations of 50-800 μM. Nickel concentrations were negatively correlated with the biomass of cotyledons, stems and roots in Luffa cylindrica seedlings. Significant increases in superoxide dismutase (SOD) activity of cotyledons, stems and roots over that of control were observed at all tested nickel concentrations. The elevated guiacol peroxidase (GPX) activity was observed in the cotyledons, stems and roots of Luffa cylindrica seedlings exposed to different levels nickel. Catalase (CAT) activity was significantly enhanced by tested nickel concentrations except for in the roots at 800 μM. Phenylalanine ammonia-lyase (PAL) activity in the cotyledons, stems and roots was significantly induced and was positively correlated to increasing nickel concentrations except for in the roots under 800 μM stresses. The present results suggested that treatment with different levels of nickel may enhance the antioxidant activities in the cotyledons, stems and roots of Luffa cylindrica seedlings, thus alleviating Ni-induced oxidative damage and enhancing Ni tolerance.