Several lines of evidence support a role of oxidative stress in the pathology of Alzheimer’s disease (AD). NAD(P)H:quinone oxidoreductase 1 (NQO1) catalyzes the two-electron reduction of quinones, preventing their participation in redox cycling and subsequent generation of reactive oxygen species. We examined association between the NQO1 C609T gene polymorphism and sporadic AD in a Chinese population comprising 311 AD patients and 330 controls. Our results showed a higher T-allele frequency in the AD cases compared with the controls. The difference was close to but did not reach statistically significant level [p = 0.059; odds ratio (OR) T versus C = 1.236; 95% confidence interval (95% CI), 0.992–1.540]. A significantly low C/C genotype frequency in the AD cases compared with the controls was detected (p = 0.025; OR C/C versus C/T + T/T = 0.674; 95% CI, 1.049–2.098) and APOE ε4 status analysis revealed significant difference in the APOE ε4 non-carriers (p = 0.036; OR = 0.633; 95% CI, 1.027–2.427). In the ≥65 years samples, significantly low C/C frequency in the AD cases in comparison with the controls was observed in the APOE ε4 non-carriers (p = 0.045; OR = 0.595; 95% CI, 1.010–2.794). These results indicated that the C/C genotype had a possible protective effect against AD development, and the T allele might be a weak risk factor for late onset AD.