Abstract Currently IFN-α is widely used for effective treatment of viral infections and several malignancies. However, IFN-α can cause neuropsychiatric disturbances and mental impairments, including fatigue, insomnia, depression, irritability and cognitive deficits. Molecular and cellular mechanisms leading to such side-effects are still poorly understood. Neurons seem to be an important target in mediating cellular effects induced by exposure to this cytokine, but so far little is known about IFN-α-induced effects on these cells. We have investigated the ability of IFN-α (2–100 ng/ml) to induce damage and toxicity to the human neuroblastoma SH-SY5Y cell line, commonly used for studying such phenomena, and the mechanisms underlying these effects. After 24 h treatment, IFN-α increased mitochondrial activity, whereas cell density was reduced in a dose- and time-dependent manner. This effect did not depend on reduced cell proliferation, but rather the activation of apoptosis, as revealed by an increased Bax:Bcl-2 mRNA ratio after 72-h IFN-α exposure. At this time-point, IFN-α also reduced the expression of the brain-derived neurotrophic factor gene, and induced an increase in reactive oxygen species (ROS). A co-treatment with N-acetyl-cysteine (NAC; 5 mm), a potent antioxidant and mitochondrial modulator, was able to counteract all of these IFN-α-induced effects. These findings demonstrated that IFN-α induces neurotoxicity and apoptosis that is, in part, very likely due to mitochondrial damages and production of ROS. We suggest that NAC, already tested for the treatment of psychiatric disorders, may be useful to prevent IFN-α-induced central side-effects in a safe and effective way.