The aim of the present study was to discover the signaling pathways associated with 2-(3-hydroxy-5-methoxy-phenyl)-6,7-methylenedioxyquinolin-4-one (YYK1)-induced apoptosis in HL-60 human leukemia cells. YYK1 induced cytotoxic effects, cell morphological changes, decreased the cell number and increased reactive oxygen species (ROS) production and loss of mitochondrial membrane potential (ΔΨm) in HL-60 cells. YYK1-induced apoptosis was confirmed by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Results from colorimetric assays and western blot analysis indicated that activities of caspase-7/-3, caspase-8 and caspase-9 were increased in YYK1-treated HL-60 cells. Western blot analysis showed that the protein levels of extrinsic apoptotic proteins (Fas/CD95, FasL and FADD), intrinsic related proteins (cytochrome c, Apaf-1, AIF and Endo G), the ratio of Bax/Bcl-2 and phosphorylated p38 MAPK were increased in HL-60 cells after YYK1 treatment. Cell apoptosis was significantly reduced after pre-treatment with N-acetylcysteine (NAC; a ROS scavenger) or diphenyleneiodonium chloride (DPI; a NADPH oxidase inhibitor). Blockage of p38 MAPK signaling by SB202190 abolished YYK1-induced Fas/CD95 upregulation and apoptosis in HL-60 cells. We conclude that YYK1 induces both of extrinsic and intrinsic apoptotic pathways via ROS-mediated activation of p38 MAPK signaling in HL-60 human leukemia cells in vitro.