Because concussions are undetectable by conventional medical imaging, their diagnosis is dependent on symptoms, which can be unreliable. Conventional diffusion-weighted imaging (DWI) can detect abnormalities in concussed individuals, but lack specificity and hence cannot provide information about the underlying neuropathology, especially during the sub-acute stage of concussions where different neuropathologies occur simultaneously. In this study, we used emerging DWI methods to disambiguate the neuropathological basis of a common concussive symptom, memory problems. We found evidence of different white-matter neuropathologies in concussed youth which contributed differently to memory problems. This study is an important step towards developing neuropathologically-informed biomarkers of concussion.