[Objective] To investigate the inhibitory effect of quercetin on cisplatin-resistant human colorectal cancer (CRC) cells SW480 and SW620 and its possible mechanism. [Methods] Cisplatin-resistant subtypes of SW480 and SW620 cells were first cultured and the effects of quercetin on cell proliferation and chemosensitivity were determined by MTT assay. Flow cytometry was used to detect apoptosis and protein blotting was used to detect the expressions of relevant proteins. [Results] MTT assay showed that quercetin at the concentrations of 80 μmol/L and 160 μmol/L significantly inhibited the proliferation of SW480 and SW620 cells. Flow cytometry results showed that the apoptosis rate was significantly higher in the cisplatin combined with quercetin group than in the other three groups. Protein blotting showed that cleaved-caspase-3 and caspase-9 expressions were significantly increased in the cisplatin combined with quercetin group. The chemotherapeutic drug sensitivity assay showed that the elevated IC50 of drug-resistant cells was decreased significantly after quercetin administration (P<0.05). [Conclusion] The present study clarifies that quercetin can increase the sensitivity of human CRC cells to cisplatin. This effect may be related to its mechanism of action in affecting cell proliferation, apoptosis and autophagy.