Abstract: Water extracts of Nannochloropsis oculata (WNO) were investigated to determine whether they exhibited neuroprotective effects against oxidative-stress-induced cell damage by 2,2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) in murine hippocampus neuronal (HT22) cells. We observed that WNO exhibited scavenging effects on hydroxyl and alkyl radicals as well as on intracellular Reactive Oxygen Species (ROS). As a consequence, WNO reduced AAPH-induced cell death, the fraction of sub-G1 cells and DNA damage in HT22 cells. The results of this study demonstrate that WNO could be used as an alternative to more toxic synthetic antioxidants as an additive in food, pharmaceutical and cosmetic preparations.