Background: The Arm Function in Multiple Sclerosis Questionnaire (AMSQ) has been developed to assess upper extremity function of patients with multiple sclerosis (MS). A minimal clinically important difference (MCID) value has not been determined yet. Objective: The objective of this study is to determine an MCID for AMSQ. Methods: We used the sensitivity- and specificity-based approach with dichotomized global perceived effect as an anchor. Results: The receiver operating characteristic (ROC) curve yielded an optimal threshold value of 14.5 (sensitivity 0.68 and specificity 0.79). The area under the ROC curve value was 0.77. Conclusion: We identified an MCID of 15 points for the AMSQ (range 31–186).