Cognitive dysfunction is frequently seen in multiple sclerosis (MS). However, there are conflicting findings regarding the factors it is associated with. To investigate the relationship between aerobic capacity, strength, disability, depression, fatigue, and cognitive reserve and function. The mobile applications Trail Making Test (TMT A-B), Digit Span Test (DST), Visuospatial Memory Test (VSMT), and Tap Fast were used in the cognitive function evaluation. Functional performance was assessed with the 6-minute walk test (6MWT), 5-Time Sit-to-Sand (5STS) test, and grip strength. Cognitive Reserve Index (CRI), Beck Depression Inventory, Fatigue Severity Scale (FSS), and Nottingham Health Profile were also used. A significant difference was found between the MS and control groups only in the 6MWT, STS-5, grip strength, TMT, VSMT, and Tap Fast. Good correlation was found between the TMT-A and 6MWT and physical mobility. A fair correlation was shown between grip strength, energy, and pain status. A good correlation was found between TMT-B and 6MWT, and a fair relationship with disability, cognitive reserve, and pain. Good correlation was observed between the DST and 6MWT, left grip strength, pain, and energy status; fair correlations were found between right grip strength, cognitive reserve, and physical mobility. Good correlation was found between the VSMT and energy. A fair relationship between disability, cognitive reserve, and pain was demonstrated. Good correlation was observed between the Tap Fast score and disability, 5STS, FSS, energy, and physical mobility. A fair relationship was found between pain and social isolation. It has been shown that cognitive performance in MS is related to disability, functional performance, cognitive reserve, fatigue, and general health. NCT06084182.