Objective: Extracellular deposition of the beta-amyloid (A beta) peptide, which is the main finding in the pathophysiology of Alzheimer's disease (AD), leads to oxidative damage and apoptosis in neurons. Melissa officinalis (M. officinalis) is a medicinal plant from the Lamiaceae family that has neuroprotective activity. In the present study we have investigated the protective effect of the acidic fraction of M. officinalis on A beta-induced oxidative stress and apoptosis in cultured cerebellar granule neurons (CGN). Additionally, we investigated a possible role of the nicotinic receptor. Materials and Methods: This study was an in vitro experimental study performed on mice cultured CGNs. CGNs were pre-incubated with different concentrations of the acidic fraction of M. officinalis for 24 hours, followed by incubation with A beta for an additional 48 hours. CGNs were also pre-incubated with the acidic fraction of M. officinalis and mecamylamin, followed by incubation with A beta. We used the 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assay to measure cell viability. Acetylcholinesterase (AChE) activity, reactive oxygen species (ROS) production, lipidperoxidation, and caspase-3 activity were measured after incubation. Hochst/annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining was performed to detect apoptotic cells. Results: The acidic fraction could protect CGNs from A beta-induced cytotoxicity. Mecamylamine did not abolish the protective effect of the acidic fraction. AChE activity, ROS production, lipid peroxidation, and caspase-3 activity increased after A beta incubation. Preincubation with the acidic fraction of M. officinalis ameliorated these factors and decreased the number of apoptotic cells. Conclusion: Our results indicated that the protective effect of the acidic fraction of M. officinalis was not mediated through nicotinic receptors. This fraction could protect CGNs through antioxidant and anti-apoptotic activities.