The aim of the study was to assess dual-task cost to spatio-temporal gait parameters in people with multiple sclerosis and a matched control group. The multiple sclerosis group was composed of 17 participants with a diagnosis of multiple sclerosis and an Expanded Disability Status Scale score of less than 6. A total of 17 healthy participants were allocated to the control group by stratification. Controls were matched on the basis of age, sex, sociocultural habits, and body structure. Dual-task cost was determined by within-group repeated-measures analysis of variance. Participants were instructed to ambulate under normal conditions and perform a discrimination and decision-making task concurrently. Then, between-group analysis of variance was used to assess differences in mean dual-task cost between groups and determine dual-task cost differential. Testing was performed using three-dimensional photogrammetry and an electronic walkway. Based on dual-task cost differential, gait cycle time increase (-5.8%) and gait speed decrease (6.3%) because of multiple sclerosis-induced impairment. During single- and dual-task conditions, gait speed was lower in multiple sclerosis participants, because of a shorter step length and increased swing time. Increased gait time might be the result of compensatory mechanisms adopted to maintain stability while walking specially during the double-support phases.