AbstractDespite the proven efficacy of the disease-modifying therapy (DMT) for multiple sclerosis (MS), the rates of non-adherence are frequently high. We aimed to evaluate the rate of non-adherence to the first DMT in Upper Egypt and identify different contributing factors. Out of 310 patients, ninety-seven adult patients with RRMS were recruited from three MS units located in Upper Egypt and were subjected to the following: complete clinical history, expanded disability status score (EDSS), Eight-item Morisky Medication Adherence Scale (MMAS-8), abbreviated Treatment Satisfaction Questionnaire for Medication-9 (TSQM-9), Hamilton depression scale, Fatigue Severity Scale (FSS) and the Pittsburgh Sleep Quality Index (PSQI). According to MMAS-8 scores, 63 (64.9%) of patients were non-adherent to their first DMT. Non-adherent patients are more likely to have longer disease duration (p = 0.002), longer duration on first DMT (p = 0.030), first DMT-start date before 2019 (p = 0.040), and lower treatment satisfaction scores (p = 0.016). However, there was no significant relation with physical disability, depression, fatigue, or sleep quality. On the regression analysis model, a lower treatment satisfaction score was the only predictor of DMT non-adherence (p = 0.012). Despite expanding DMT options, non-adherence among MS patients in Upper Egypt is high. Treatment satisfaction with DMT is the only predictor of adherence among MS patients of Upper Egypt. Adherence and satisfaction with the prescribed DMT should be assessed carefully to maximize DMT benefits.