The 5-lipoxygenase (5LO) enzyme is widely distributed within the central nervous system. Previous works showed that this protein is upregulated in Alzheimer's disease, and that its genetic absence results in a reduction of amyloid beta levels in Tg2576 mice. However, its contribution to tau pathology remains to be investigated. To this end we studied the effect of 5LO chronic pharmacologic inhibition on endogenous tau level and metabolism in the same mice. The phosphorylation of tau at S396 and S396/404 in the brains of mice receiving zileuton, a selective and specific 5LO inhibitor, was significantly reduced when compared with their controls, while there was no significant change of tau phosphorylation at S202/T205, T231/S235, and T181 epitopes. The 5LO-dependent reduction of tau phosphorylation resulted from a significant decrease in the level and activity of the cyclin-dependent kinase-5 but not other kinases. Our findings highlight the novel functional role that neuronal 5LO plays in modulating tau phosphorylation, and suggest that pharmacologic inhibition of 5LO could provide a novel therapeutic opportunity also for Alzheimer's disease-related tau pathology.