BACKGROUND : Prazosin, a non-selective α1-adrenoceptor and a selective α2B-adrenoceptor antagonist, is reported to possess anti-cancer activity in some types of cancer. The aim of this study was to investigate the effect of prazosin on acute myeloid leukemia (AML) and the underlying relevant mechanisms. METHODS : AML cell lines U937 and HL60 were treated with different concentration of prazosin (5, 10 and 15 μM), CCK8 and flow cytometry assays were performed to examine the effects of prazosin on cell viability, cell cycle distribution and apoptosis. Western blot assay was used to detect the expression of related proteins. RESULTS : We observed that prazosin inhibited cell viability of U937 and HL60 cells and induced the rate of apoptosis in a dose-dependent manner, as well as induced cell cycle arrest at G1 phase. The activation of PI3K/Akt/mTOR signaling pathway was significantly suppressed by prazosin via reducing the phosphorylation of Akt and mTOR. Moreover, by RNA-seq analysis, we found that the expression of tensin 1 (TNS1) was down-regulated by prazosin, and down-regulation of TNS1 could inhibit cell viability of U937 and HL60 cells, as well as induced cell apoptosis. The PI3K/Akt/mTOR signaling pathway was also suppressed by depletion of TNS1. Furthermore, up-regulation of TNS1 could reverse the effects of prazosin on viability and apoptosis in U937 and HL-60 cells, as well as the PI3K/Akt/mTOR signaling pathway. CONCLUSIONS : These results highlight an anti-cancer activity of prazosin on AML by inhibiting the PI3K/Akt/mTOR pathway and targeting TNS1.