A novel nonvolatile rewritable memory device based on the soluble poly(N-vinylcarbazole)-chemically modified MoS2 nanosheets (MoS2-PVK) was fabricated with the configuration of Au/MoS2-PVK/ITO. This is the first example of polymer covalently modified MoS2 nanosheet-based memory devices. As expected, this device exhibited a typical storage performance of nonvolatile rewritable memory, with a turn-on voltage of -1.54 V and an ON/OFF current ratio of 4 × 102. After annealing at 80 °C for 1 h under a nitrogen atmosphere, a high ON/OFF current ratio (up to 3 × 104) and a lower turn-on voltage (-1.31 V), which are among the best reported for MoS2-based polymer/organic memory devices, were achieved due to enhanced crystallization of PVK, which induced a more efficient intramolecular charge transfer effect between PVK and MoS2 during the annealing process. The effect of film thickness on the current-voltage characteristics of the MoS2-PVK-based devices and the memory performance of the MoS2/PVK blends-based devices have also been explored.