Background: Multiple sclerosis (MS) is a chronic immune-mediated neurological disease affecting mainly young adults. MS patients are more prone to disability progression affecting their physical and psychological health, so understanding factors that may affect their adherence to disease modifying therapy (DMT) will help for better medication choice. Objectives: To realize the degree of DMT adherence among MS patients in Egypt. To find the barriers contributing to medication adherence. To evaluate the clinical impact of non-adherence on MS patients. Methods: This cross-sectional study was carried out on 150 MS patients from MS unit at Menoufia university hospitals and Nasser institute for research and treatment hospital. The degree of adherence was measured using the Arabic version of eight-item Morisky Medication Adherence Scale (MMAS-8). Other related variables were measured by a questionnaire including socio-demographic data, disease characteristics and previous treatment data. Results: A total of 150 MS patients were included with mean age ± standard deviation of 32.5±8 years and 78% females. The degree of adherence was (59%). The adherence to DMT was significantly affected by the DMT type and route of administration, MS phenotypes, line of treatment and patient satisfaction (P<0.05). However, the adherence was not affected by degree of disability measured by patients' current EDSS, median (3.415) in adherent patients and (3.395) in non-adherent patients. The most common causes of non-adherence were forgetfulness (40.3%) and injection site reaction/flu like symptoms (38.7 %). Non-adherent patients had higher number of recurrent hospitalization and relapses (median, 1 vs. 0 times, P<0.05) and shorter time from the last hospitalization compared to adherent patient (mean, 10.5 vs. 14 months, P<0.05). Conclusions: Many factors affect Adherence to DMT and Non-adherent patients experienced significantly more relapse rate and recurrent hospitalization.