Curcumin, derived from the food flavoring spice turmeric (Curcuma longa), has been shown to exhibit anticancer activities and induce apoptosis in many types of cancer cell lines. In our previous study, curcumin was able to inhibit murine myelomonocytic leukemia WEHI-3 cells in vivo. However, there is no report addressing the cytotoxic responses and the mechanisms underlying curcumin-induced apoptotic cell death in WEHI-3 cells. Therefore, we hypothesized that that curcumin affected WEHI-3 cells and triggered cell death through apoptotic signaling pathways. The effects of curcumin on WEHI-3 cells were investigated by using flow cytometric analysis, comet assay, confocal laser microscopy and Western blotting. In this study, we found that curcumin induced apoptosis in WEHI-3 cells in a dose-dependent (5–20 μM) manner. Interestingly, curcumin enhanced the level of the antiapoptotic protein Bcl-2 which might show that curcumin-induced apoptosis is done through the ER stress signaling pathways based on the increase of CIEBP homologous protein (CHOP), activating transcription factor 6 (ATF-6), inositol-requiring enzyme 1 (IRE1), and caspase-12 in WEHI-3 cells. Moreover, curcumin increased the reactive oxygen species (ROS) production and cytosolic Ca2+ release, and induced DNA damage, but decreased the level of mitochondrial membrane potential (ΔΨm) in WEHI-3 cells. In conclusion, curcumin-induced apoptosis occurs through the ROS-affected, mitochondria-mediated and ER stress-dependent pathways. The evaluation of curcumin as a potential therapeutic agent for treatment of leukemia seems warranted. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2013.