A first-in first-out (FIFO) memory device includes a main FIFO unit, an auxiliary FIFO unit and a control unit. The main FIFO unit includes first through N-th one-port memories, each of which including M entries, where N and M are integers greater than or equal to two. The auxiliary FIFO unit includes one dual-port memory having M entries. The control unit performs a write operation by receiving a write command and data and storing the data in one of the main FIFO unit and the auxiliary FIFO unit based on an operating mode, and performs a read operation by receiving a read command and reading the data from one of the main FIFO unit and the auxiliary FIFO unit based on the operating mode.