Background: Multiple Sclerosis (MS) is a progressive neurodegenerative disease associated with demyelination of the central nervous system which negatively impacts both motor and cognitive function. Not surprisingly, persons with MS have difficulty performing two tasks, such as a motor and a cognitive task, simultaneously. Declines in dual-tasking have been linked with falls. As a result, dual-task assessment with the Walking While Talking Test (WWTT) is commonly utilized in the clinical setting; however, the validity and minimal detectable change of the WWTT has not been established for persons with MS. Objectives: The primary objective of the study was to establish the WWTT as a valid measure of dual-task function by examining concurrent validity with other motor, cognitive and dual-task measures, and to establish the minimal detectable change for both the simple and complex conditions of the WWTT. Methods: In a single visit, 38 adults (34 female, mean age 49.8(±9.1), PDDS (Patient Determined Disease Steps) mean 3, range 6) completed the WWTT simple (walk while reciting the alphabet) and complex (walk while reciting every other letter of the alphabet) conditions as well as a battery of cognitive and motor tests validated for persons with MS. Spearman correlations were used to examine concurrent validity. The sample was also split into low and high disability groups to observe the impact of disability severity on relationships among WWTT and cognitive and motor function. Results: Excellent concurrent validity (p<.001) was observed for the WWTT simple and complex and the motor and dual-task measures: timed up-and-go, timed 25-foot walk, forward walking velocity, backward walking velocity, six-spot step test, and timed up-and-go-cognitive. Group data showed concurrent cognitive results for the WWTT-simple and the symbol digit modalities test (SDMT, p=.041), and significant concurrent validity with the WWTT-simple CVLT (California Verbal Learning Test) total recall, and SDMT (p=.045) within the low PDDS group. Results support the validity and use of the WWTT to research cognitive and motor performance and DTEs in persons with MS. Minimal detectable change values were also established for both WWTT conditions. Conclusions: The WWTT is a quick, easy-to-administer clinical measure that captures both motor and cognitive aspects of performance for persons with MS. Clinicians should consider adding the WWTT to the evaluation of persons with MS to examine dual-task performance.