Amaranth oil has several health benefits. It has lipid lowering, anti-diabetic, immune modulatory and cytoprotective properties, activates the function of mitochondria and improves heart rate variability. It has been suggested that the effect of amaranth oil on redox status is involved in this multitude of cellular and clinical influences of the oil. We examined whether amaranth oil can modify free radical production. EPR experiments with amaranth oil dissolved in DMSO showed scavenging of carbon centered radicals but not of oxygen centered radicals. Moreover, a concentration dependent scavenging effect of amaranth oil on ultrasound-induced radicals was observed. However, in adrenaline autoxidation experiments amaranth oil showed a strong prooxidant action through activation of superoxide anion formation. This two-sided effect of amaranth oil, i.e. both anti- and pro-oxidant action, was corroborated in human lung fibroblasts that were exposed to amaranth oil. At low concentrations of amaranth oil, fibroblasts were protected against oxidative stress, whereas in incubations with high amaranth oil concentrations more H2O2-induced intracellular radical damage was found. We suggest that mild pro-oxidant activity could be the underlying mechanism in the health beneficial effect of amaranth oil.