Fungal metabolite, gliotoxin is an epipolythiodioxopiperazin (ETP) class and has various roles including immunomodulatory and apoptotic effects. This study was designed to evaluate the mechanism by which gliotoxin exerts the apoptosis on human promyelocytic leukemic HL-60 cells. Herein, we demonstrated that the gliotoxin decreased the cell viability in a time-dependent manner Gliotoxin-induced cell death was confirmed us apoptosis characterized by chromatin condensation and ladder-pattern fragmentation of genomic DNA. Gliotoxin increased the catalytic activities of caspase-3 and caspase-9. Activation of caspase-3 was further confirmed by degradation of procaspase-3 and poly(ADP-ribose) polymerase (PARP) by gliotoxin in HL-60 cells. Furthermore, gliotoxin induced the changes of mitochondrial transmembrane potential (MTP). Antioxidants, including GSH and NAC, markedly inhibited apoptosis with conistent suppression of enzymatic activity of caspase-3, caspase-9, and MTP loss in gliotoxin-treated cells. Taken together, we suggest that gliotoxin function as an oxidant and ploys proapoptotic roles in HL-60 cells via activation of intrinsic caspase cascades as well as mitochondrial dysfunction.