Natural polyphenols, such as resveratrol, have beneficial functions on major human diseases such as cancer, diabetes, and cardiovascular disease. Besides acting as antioxidants, some of these polyphenols can also target proteins to modulate specific biological pathways. The lysine-specific histone demethylase LSD1 plays important roles in cell growth, differentiation and nutrient metabolism. Here, we studied the effect of natural polyphenols resveratrol, curcumin, quercetin and analogs on LSD1. Using LSD1 enzymatic assays, we show that resveratrol, curcumin and quercetin displayed a potent inhibitory effect on the LSD1 activity and were more potent than the known LSD1 inhibitor trans-2-phenylcyclopropylamine (TCP). The new function of resveratrol, curcumin and quercetin is independent of their antioxidant properties, as other antioxidants had no effect on LSD1 under the similar conditions. In C2C12 fibroblasts, resveratrol and curcumin can efficiently inhibit myogenic expression and differentiation, for which LSD1 is required. Thus, our study has identified LSD1 as a novel target of bioactive natural compounds, such as resveratrol, curcumin and quercetin, and such finding suggests that LSD1 inhibition can at least partially contribute to some of the previously observed beneficial effects of these compounds.