With increasing use of plant-based cancer chemotherapeutic agents, exploring the antiproliferative effects of phytochemicals has gained increasing momentum for anticancer drug design. The present study was undertaken to investigate the effect of root bark of Juglans regia (RBJR) organic extracts on cell proliferation, and to determine the molecular mechanism of RBJR-induced cell death by determining the expression of Bcl-2, Bax, caspases, Tp53, Mdm-2 and TNF-α in MDA-MB-231 human breast cancer cells. The results demonstrate that WNRB suppressed proliferation and induced apoptosis in a dose and time dependent manner by modulating expression of key genes. This involved characteristic changes in cytoplasmic and nuclear morphology, DNA fragmentation (TUNEL assay), levels of mRNA and expression of corresponding proteins. Real Time PCR and western blot analysis revealed that the expression of of Bax, caspases, tp53, and TNF-α was markedly increased in MBA-MB-231 cells treated with the RBJR extract. In contrast Bcl2 and mdm-2 expression was down regulated after exposure. In summary, our data suggest the presence of bioactive compound(s) in WNRB capable of killing breast carcinoma cells through induction of apoptosis, and therefore a candidate source of anticancer drugs. © 2017 Elsevier B.V., All rights reserved.