A non-volatile memory device, related memory system, and program method for the non-volatile memory device are disclosed. In the method, memory cells in a memory cell array are accessed through a plurality of word lines by applying a program voltage to a selected word line, wherein the selected word line is not adjacent to an outmost word line, applying a first reduced pass voltage to word lines adjacent to the selected word line, and applying a second reduced pass voltage to the outermost word lines.