The poor prognosis of patients with acute myeloid leukemia (AML) is largely ascribed to the deficiency of persistently effective therapies. Despite the recent approval of targeted drugs such as the BCL-2 inhibitor venetoclax, the clinical benefit is limited due to the development of resistance. The use of natural products is emerging as a feasible strategy to treat malignant diseases including AML. Flavokawain A (FKA) is a naturally occurring chalcone isolated from the root of kava and possesses extensive antitumor activities. The therapeutic potential of FKA in AML remains unknown. In the present study, we found that treatment with FKA reduced the viability in four AML cell lines in dose- and time-dependent manners. The anti-AML activity of venetoclax was significantly potentiated by FKA. Mechanistically, FKA induced G1 phase arrest in AML cells along with CDT1 downregulation and p27 upregulation. Knockdown of CDT1 increased the expression of p27, leading to the inhibition on cell viability. Both p27 upregulation and viability inhibition caused by FKA was partially rescued by CDT1 overexpression. The therapeutic effect of FKA alone or in combination with venetoclax was verified in primary blasts from AML patients, further strengthening the clinical relevance of the current study. Therefore, our data suggest that FKA can be considered as a potential therapeutic agent in the treatment of AML.