Oxidative stress is considered one of the factors that cause dysfunction and damage of neurons, causing diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer’s disease (AD), and Parkinson’s disease (PD).Recently, natural antioxidant sources have emerged as one of the main research areas for the discovery of potential neuroprotectants that can be used to treat neurological diseases. In this research, we assessed the neuroprotective effect of a 70% ethanol Salvia miltiorrhiza Radix (SMR) extract and five of its constituent compounds (tanshinone IIA, caffeic acid, salvianolic acid B, rosmarinic acid, and salvianic acid A) in HT-22 hippocampal cells. The experimental data showed that most samples were effective in attenuating the cytotoxicity caused by glutamate in HT-22 cells, except for rosmarinic acid and salvianolic acid B. Of the compounds tested, tanshinone IIA (TS-IIA) exerted the strongest effect in protecting HT-22 cells against glutamate neurotoxin. Treatment with 400 nM TS-IIA restored HT-22 cell viability almost completely. TS-IIA prevented glutamate-induced oxytosis by abating the accumulation of calcium influx, reactive oxygen species, and phosphorylation of mitogen-activated protein kinases. Moreover, TS-IIA inhibited glutamate-induced cytotoxicity by reducing the activation and phosphorylation of p53, as well as by stimulating Akt expression. This research suggested that TS-IIA is a potential neuroprotective component of SMR, with the ability to protect against neuronal cell death induced by excessive amounts of glutamate.