Provided are memory devices and memory programming methods. A memory device may include a multi-bit cell array including a plurality of multi-bit cells, a programming unit configured to program a first data page in the plurality of multi-bit cells and to program a second data page in the multi-bit cells with the programmed first data page, a first controller configured to divide the multi-bit cells with the programmed first data page into a first group and a second group, and a second controller configured to set a target threshold voltage interval of each of the multi-bit cells included in the first group based on first read voltage levels and the second data page, and to set a target threshold voltage interval of each of the multi-bit cells included in the second group based on second read threshold voltage levels and the second data page.