A novel doxorubicin-quantum dots-folate nanoconjugate with activatable fluorescence and cytotoxicity was prepared and used as a fluorescence probe for the targeted imaging of cancer cells. After the targeted folate receptor induced the intracellular uptake of the nanoconjugate and glutathione-mediated dissociation, the nanoconjugate became activated, showing enhanced fluorescence and cellular toxicity within the cell.