Background: The Sensoready® pen is intended for self-administration of subcutaneous 20 mg ofatumumab at home. This human factors summative study assessed the usability of the Sensoready pen in relapsing multiple sclerosis patients. Methods: 32 patients (injection-experienced [n = 17] and injection-naive [n = 15]) across five locations in the USA were asked to complete two simulated injections using the Sensoready pen. Results: In the first and second simulated injections, 90.6 and 96.9% of patients, respectively, successfully delivered a full dose, while 81.3 and 84.4%, respectively, successfully performed the injection without any use errors. Conclusion: The Sensoready pen is safe and effective for its intended use by intended users and in the intended use environment. This pen has a low harm potential and high injection success rate in patients, even without prior training or experience.