Clerodendrum inerme is traditionally used for the treatment of various diseases including cancer. The present study aimed to analyze colchicine like metaphase (c-metaphase) and cell cycle delay-inducing effects of the leaf aqueous extract of C. inerme (LAECI) in onion root tip cells. Onion root growth retardation, mitotic index reduction, decreased anaphase, and telophase cumulative frequencies were analyzed for LAECI induced cell cycle delay. The LAECI (1–8 mg mL⁻¹) induced a concentration-dependent onion root growth retardation (p＜0.01), increased c-metaphase frequency at 4 h treatment, and 4 h treatment +16 h recovery in water. The LAECI could induce a reduction rate of transition from metaphase to anaphase, decreased percentage of anaphase-telophase cumulative frequency, root tip swelling and that was comparable with the colchicine action. In summary, LAECI contains secondary metabolites having c-metaphase and cell cycle delay-inducing effects in onion root tip cells.