Given the increasing incidence of gastric cancer and its high rate of metastasis, drug resistance and the mortality rate remain high. Ocimum gratissimum, a botanical species of Ocimum known to exhibit general anti-inflammatory, antioxidant, and anticancer activities has not yet been evaluated for gastric cancer proliferation. In this study, we have demonstrated that O. gratissimum extract significantly reduces the viability of gastric cancer cells by triggering apoptosis, elevating levels of ROS, and enhanced cleavage of poly-ADP-ribose polymerase and caspase-3. Western blot analysis indicated that O. gratissimum extract enhanced the cleavage of PARP and caspase-3. Moreover, O. gratissimum extract inhibited extracellular signal-regulated kinase 1/2 and increased activities of p38, a stress stimulated kinase. In conclusion, our findings show that O. gratissimum extract may be a potential antigastric cancer agent.