Inhibiting interleukin-6 (IL-6) has been postulated as an effective therapy in the pathogenesis of several inflammatory diseases. In this study, seven flavonoids were isolated from the methanol extracts of Psoralea corylifolia by bioactivity-guided fractionation. The structures of bakuchiol (1), bavachinin (2), neobavaisoflavone (3), corylifol A (4), corylin (5), isobavachalcon (6), and bavachin (7) were determined by spectroscopic analysis (¹H-, ¹³C- NMR and MS). We demonstrated that compounds 1–7 showed an inhibitory effect on IL-6-induced STAT3 promoter activity in Hep3B cells with IC₅₀ values of 4.57 ± 0.45, 3.02 ± 0.53, 2.77 ± 0.02, 0.81 ± 0.15, 1.37 ± 0.45, 2.45 ± 0.13, and 4.89 ± 0.05 µΜ, respectively. These compounds also inhibited STAT3 phosphorylation induced by IL-6 in Hep3B cells. Overall, several flavonoids from P. corylifolia might be useful remedies for treating inflammatory diseases by inhibiting IL-6-induced STAT3 activation and phosphorylation.