Provided are a memory device and a memory controller, which are configured to repair a weak word line, and a method of operating a storage device including the memory device and the memory controller. A memory device includes a memory cell array including a plurality of normal word lines and at least one spare word line, and a repair controller configured to set memory cells connected to at least one weak word line to a first operation mode and further configured to set memory cells connected to the at least one spare word line to a second operation mode. The at least one weak word line is detected from among the normal word lines based on a test result.