Styrylquinazolines are synthetic analogues of resveratrol and have been suggested to cause anti-inflammatory activity by modulating prostaglandin E₂ (PGE₂) production. In the present study, we evaluated cytotoxic effects of various styrylquinazoline derivatives and found that (E)-8-acetoxy-2-[2-(3,4-diacetoxyphenyl)ethenyl]-quinazoline (8-ADEQ) most potently inhibited the proliferation of the human cervical carcinoma HeLa cells. Exploring the growth-inhibitory mechanisms of 8-ADEQ, we found that it causes a cell cycle arrest at the G₂/M phase by DNA flow cytometric analysis, which was accompanied by upregulation of cyclin B1 expression and cyclin-dependent protein kinase 1 (Cdk1) phosphorylation. In addition, we observed that 8-ADEQ causes phosphorylation of the cell division cycle 25C (Cdc25C) protein through the activation of checkpoint kinases 1 (Chk1) and Chk2, which in turn were activated via ataxia telangiectasia mutated (ATM)/ataxia telangiectasia-Rad3-related (ATR) kinases in response to the DNA damage. Furthermore, ATM/ATR inhibitor caffeine, p53- or ATM/ATR-specific siRNA significantly attenuated 8-ADEQ-induced G₂/M arrest. These results suggest that the 8-ADEQ inhibits the proliferation of human cervical cancer HeLa cells by DNA damage-mediated G₂/M cell cycle arrest. 8-ADEQ‑induced G₂/M arrest is mediated by the activation of both Chk1/2-Cdc25 and p53-p21CIP1/WAF1 via ATM/ATR pathway, and indicates that 8-ADEQ appears to have potential in the treatment of cervical cancer.