This article reports on the design of a two-arm, randomised controlled trial of neuropsychological assessment with feedback as a direct therapeutic intervention to improve psychological wellbeing in multiple sclerosis (MS). MS patients and their caregivers are randomly allocated to one of two groups: neuropsychological assessment with feedback (the intervention), or ‘sham wait-list’ control. The trial investigates: (1) whether the intervention directly benefits patients by leading to improved knowledge of their own specific cognitive strengths and weaknesses, and improved use of adaptive psychological strategies for coping with MS; and (2) whether the intervention directly benefits caregivers by leading to improved knowledge of the patients’ specific cognitive strengths and weaknesses, and to a more positive caregiving outcome. A range of primary and secondary measures is used to evaluate these outcomes. The protocol utilises a wait-list control method which is structured to effectively blind patients and caregivers to their group allocation. Publishing the protocol prior to the results of the trial being available has a number of important methodological benefits, and informs the research community of the work that is under way to allow for collaboration and to reduce duplication of research effort. (This trial has been registered on the ANZCTR; ACTRN12612000161820.)