Although nanocarriers hold promise for cancer chemotherapy, their intracellular drug delivery pathways are not fully understood. In particular, the influence of nanocarrier stability on cellular uptake is still uncertain. By physically loading hydrophobic FRET probes, we revealed different intracellular drug delivery routes of self-assembled and disulfide bonded micelles. The self-assembled micelles were structurally dissociated by micelle–membrane interactions, and the hydrophobic probes were distributed on the plasma membrane. Alternatively, intact disulfide bonded micelles carrying hydrophobic probes were internalized into cancer cells via multiple endocytic pathways. Following internalization, disulfide bonded micelles were decomposed in early endosomes by glutathione-mediated disulfide bond reduction, exposing the probes to intracellular organelles.