As an important epigenetic regulator, histone lysine specific demethylase 1 (LSD1) has become an attractive target for the discovery of anticancer agents. In this work, a series of tranylcypromine-based derivatives were designed and synthesized. Among them, compound 12u exhibited the most potent inhibitory potency on LSD1 (IC 50 = 25.3 nM), and also displayed good antiproliferative effects on MGC-803, KYSE450 and HCT-116 cells with IC 50 values of 14.3, 22.8 and 16.3 μM, respectively. Further studies revealed that compound 12u could directly act on LSD1 and inhibit LSD1 in MGC-803 cells, thereby significantly increasing the expression levels of mono-/bi-methylation of H3K4 and H3K9. In addition, compound 12u could induce apoptosis and differentiation, inhibit migration and cell stemness in MGC-803 cells. All these findings suggested that compound 12u was an active tranylcypromine-based derivative as a LSD1 inhibitor that inhibited gastric cancer. [Display omitted] • Novel tranylcypromine-based derivatives were designed and synthesized. • Compound 12u showed low nanomolar IC 50 value against LSD1 and high selectivity for MAO-A and MAO-B. • Compound 12u suppressed LSD1 and induced the accumulation of H3K4 Me1/2 and H3K9 Me2/3. • Compound 12u induced apoptosis and differentiation, and inhibited migration and cell stemness. [ABSTRACT FROM AUTHOR]