Since Nordihydroguaiaretic acid (NDGA), a potent natural antioxidant, can produce oxidation in several cell kinds, mainly by superoxide anion production (O2), the current study was designed to assess its capacity to produce or not this reactive oxygen species on Vero cell line, with the aim to establish whether this lignan behaves as a pro- or antioxidant. The O2 production was determined by the Nitro Blue Tetrazolium reduction test. Results show that NDGA has a dual-face behavior on this eukaryotic cell model depending on the biological environment and its concentration. The NDGA behaved as a pro-oxidant when it was tested single, by means of an increase in O2 production that was directly concentration-dependent. Mixed with an antioxidant (ascorbic acid) or a moderate oxidant (glucose), the NDGA behaved as pro-xidant at low concentrations and antioxidant at high concentrations.