Scutellaria is a genus of Lamiaceae with known antiproliferative potentials. Scutellaria litwinowii Bornm. & Sint. ex Bornm. is one of the Iranian species of Scutellaria. Although there are widespread reports about the cytotoxic and antitumor effects of some species of this genus, research on the molecular mechanism responsible for the anticancer effects of S. litwinowii has not yet been conducted. In the current study, the apoptotic effects of S. litwinowii on 2 myeloid cell lines, apoptosis-proficient HL60 cells and apoptosis-resistant K562 cells, were analyzed. An increase in the activity of caspases-3, -8, and -9, poly (ADP ribose) polymerase (PARP) cleavage, detection of phosphatidylserine on the outer layer of cell membrane and sub-G1 peak in the flow cytometry histogram of treated cells, suggested the induction of apoptosis. S. litwinowii also increased the Bax/Bcl-2 ratio. It could be concluded that S. litwinowii induced apoptosis in both apoptosis-proficient and apoptosis-resistant leukemic cells and it might be considered as a novel candidate in the treatment of hematological malignancies.