Psoralen is a major active component of Psoralea corylifolia. In the present study, we analyzed psoralen-induced changes in human breast cancer MCF-7/ADR cells and investigated the underlying mechanisms of the anticancer effect on MCF-7/ADR cells. We measured cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to evaluate the cytotoxicity and multidrug resistance (MDR) reversal activity of psoralen. The cell cycle distribution and apoptosis, accumulation and efflux of rhodamine123 (Rh123), and P-glycoprotein (P-gp) expression levels of MCF-7/ADR cells treated with psoralen were all detected by flow cytometry (FCM). We assessed P-gp ATPase activity by monitoring ATP consumption. We evaluated the activity of nuclear factor-kappaB (NF-κB) and the expression of E-cadherin, vimentin and α-smooth muscle actin (SMA) involved in regulating epithelial–mesenchymal transition (EMT). The results showed that psoralen inhibited the proliferation of MCF-7/ADR cells as shown by G0/G1 phase arrest rather than encouraging apoptosis. It was also observed that psoralen reversed MDR through inhibiting ATPase activity rather than reducing P-gp expression. Our results further showed that psoralen inhibited the migration abilities of MCF-7/ADR cells by repressing EMT possibly through inhibiting the activation of NF-κB. Our findings provided a systematic and detailed description of the anti-cancer effect of psoralen on MCF-7/ADR cells for the exploration of natural compounds as novel anticancer agents.