One of the hallmark features of multiple sclerosis (MS) involves the impairment of walking. The impairment of walking becomes particularly concerning when it co-occurs with an increase in physiological energy expenditure, and this process is expressed as the energetic or oxygen (O₂) cost of walking. This review presents data on the O₂ cost of walking in MS, including comparisons with healthy controls, its association with other factors that represent influences and consequences, and approaches for management. We end the paper by identifying limitations of the existing research and potential directions for future examinations of the O₂ cost of walking in MS.