Thevetiaflavone could upregulate the expression of Bcl?2 and downregulate that of Bax and caspase?3. Bcl-2 Bax Caspase-3 Thevetiaflavone, a natural flavonoid obtained from Wikstroemia indica, could improve cell viability and suppresses the leakage of lactate dehydrogenase from the cytoplasm. Further investigation of the mechanisms demonstrated that Thevetiaflavone decreases overproduction of ROS and ameliorates ROS?mediated mitochondrial dysfunction, including collapse of mitochondrial membrane potential and mitochondrial permeability transition pore opening. Thevetiaflavone reduces the intracellular Ca2+ level, which is closely associated with mitochondrial function and interplays with ROS. Furthermore, Thevetiaflavone inhibits apoptosis in PC12 cells through upregulating the expression of Bcl?2 and downregulating that of Bax and caspase?3 in addition to increasing the activity of caspase?3. These results further indicate the protective effects of thevetiaflavone in vivo and its application in the clinic.