A memory system includes a first dual in-line memory module (DIMM), a second DIMM, and a controller. The first DIMM may include a first memory device including a first on-die termination (ODT) circuit connected to a data line. The second DIMM may include a second memory device including a second ODT circuit connected to the data line. The controller is connected to the first and second memory devices through the data line, generates first and second delay information, and determines whether to change an ODT duration of the first or second ODT circuit using the first and second delay information. The first delay information is indicative of a time taken for command/address or clock signals to reach the first memory device. The second delay information is indicative of a time taken for command/address signal or clock signals to reach the second memory device.