In method of programming a nonvolatile memory device including a plurality of multi-level cells that store multi-bit data according to example embodiments, a least significant bit (LSB) program operation is performed to program LSBs of the multi-bit data in the plurality of multi-level cells. A most significant bit (MSB) program operation is performed to program MSBs of the multi-bit data in the plurality of multi-level cells. To perform the MSB program, an MSB pre-program operation is performed on first multi-level cells, from among the plurality of multi-level cells, that are to be programmed to a highest target program state among a plurality of target program states, and an MSB main program operation is performed to program the plurality of multi-level cells to the plurality of target program states corresponding to the multi-bit data.