The invention discloses a data storage device and a method for reducing the firmware update time and a data processing system including the device. The data storage device for reducing a firmware update time includes a non-volatile memory configured to store a firmware update image which will replace a current firmware image, a first volatile memory, and a processor configured to control an operation of the non-volatile memory and an operation of the first volatile memory. When a first code included in the current firmware image is executed by the processor, the first code generates data necessary for an operation of the data storage device and stores the data in the first volatile memory. When a second code included in the firmware update image is executed by the first code, the second code accesses and uses the data that has been stored in the first volatile memory.