A memory module includes a circuit board, a plurality of memory devices, and a power management integrated circuit (PMIC). The circuit board includes first connectors, a second connector, and a third connector connected to an external device. The plurality of memory devices are mounted on the circuit board, and connected to the first connectors. The PMIC receives a first voltage through the second connector, generates a second voltage using the first voltage, and provides the second voltage to the plurality of memory devices The PMIC adjusts the second voltage based on a signal received through the third connector such that a voltage difference of the first voltage and the second voltage is reduced in a training mode of the memory module.