Scientists are constantly searching for phytochemicals and compounds with anti-cancer and antioxidant activity. In this study, the anti-proliferative activity of plant extracts from Origanum majorana (marjoram) was tested on human lymphoblastic leukemia cell line Jurkat. Cytotoxicity was examined using non-radioactive cytotoxicity assay and the IC(50) was calculated. At non-cytotoxic concentrations, the viability of cells decreased with increase of concentration of plant extract. The anti-proliferative effect was also found to be dose-dependent. Analysis via flow cytometry shows that marjoram extracts stimulated apoptosis. Induction of apoptosis was caused by an up-regulation of p53 protein levels and down-regulation of Bcl-2alpha. Marjoram exhibited a strong scavenging activity (SC(50)=0.03mg dry weight). The conclusions from this study suggest that marjoram extracts exhibit anti-proliferative effect and high antioxidant activity. For that it merits further investigation as a potential therapeutic agent.