Patients may refuse, be unable to use, or show nonresponse to conventional steroid treatment of multiple sclerosis (MS) exacerbation. Adrenocorticotropic hormone (ACTH), one of several melanocortin peptides with mechanisms of action beyond steroidogenesis, should be reconsidered in the treatment of MS exacerbations. The current case report presents the treatment outcome of a patient with new-onset MS exacerbation treated with ACTH following lack of response to steroid treatment. A 49-year-old female presented with slurred speech, blurry vision, off-balance feeling, and possible left-sided mild internuclear ophthalmoplegia. Magnetic resonance imaging showed findings typical for primary demyelinating disease. Despite 5-day high-dose intravenous methylprednisolone treatment, the patient's symptoms worsened, including right-sided facial weakness, gait instability that required unilateral support, drooling, and new dorsal pontine white matter lesion on magnetic resonance imaging. Treatment with ACTH gel 80 U for 5 consecutive days resulted in patient functional improvement, including vision and gait. ACTH gel treatment stabilized disease progression, allowing the initiation of long-term disease-modifying treatment with monthly intravenous natalizumab. Effects of melanocortin signaling on immune function and inflammation beyond steroidogenesis provide a basis for understanding the clinical experience with ACTH gel treatment in patients with MS exacerbation.