BackgroundFace masks protrude into the lower visual field causing reduced perception of visual stimuli, potentially making obstacle avoidance during walking more difficult and increasing fall risk. Recommendations on walking and mask wearing for older adults have been debated, with no clear consensus on the various factors interacting and influencing walking safety while wearing a face mask. It is particularly important to address this issue in populations at an increased risk of falls. Therefore, this study aims to investigate the effects of mask-wearing on objectively measured walking adaptability in people with Parkinson’s disease and Multiple Sclerosis.Methods50 patients with either Parkinson’s disease or Multiple Sclerosis attending inpatient neurorehabilitation will be recruited to participate in this crossover study. Performance during a standardized gait adaptability (C-Gait) test on a VR-based treadmill (C-Mill+VR), as well as during clinical mobility tests (10-meter walk test, Timed Up & Go test, and stair ambulation) will be measured with and without an FFP2- mask (order randomized). In addition, participants will be asked about their perceived performance and perceived safety during the tests with and without a mask. Performance on the seven C-Gait subtests is based on centre of pressure-derived measures of foot placement in relation to the different tasks. These are averaged and added to a cognitive C-Gait task to give the overall composite score (primary outcome). Secondary outcomes will include the different subscores and clinical mobility tests.Potential significanceThis study will make an important contribution to an ongoing debate regarding recommendations persons with and without a neurological disease should be given regarding wearing a face mask while walking. Furthermore, the study will complement the existing scientific discourse with clinical data from people with a neurological disease for whom falls, mobility deficits and mask wearing may be more frequent, which can help inform evidence-based recommendations.Trial registrationGerman clinical trial register:DRKS00030207.