A method of writing data in a non-volatile memory device includes receiving a program command and a first row address corresponding to a first word line; performing a first partial programming operation with respect to first memory cells coupled to the first word line; performing a second partial programming operation with respect to second memory cells coupled to a second word line adjacent to the first word line; performing a first verification operation by verifying the first partial programming operation; and selectively performing a first additional programming operation with respect to the first memory cells depending on a result of the first verification operation.