Objective: Multiple Sclerosis (MS) is a chronic disease of the central nervous system that affects young adults and women more. Although it is not seen as a fatal disease, it is associated with earlier mortality despite developing treatment options. Methods: Patients who were diagnosed with clinically definite MS and followed up between January 2001 and January 2021 were included in the study. The data were obtained from the IMED database. Patients with and without mortality were compared. Age, gender, age, disease onset type, disease duration, MS subtype, total number of attacks, final EDSS value, immunomodulatory treatment status, comorbid diseases and mortality reasons were recorded. Results: 2456 patients were included in the study. Mortality was detected in 26 patients within 20 years of follow-up. The female / male ratio of patients with mortality was 3.33. The mean age of patients without mortality was found to be 41.97 ± 12.02, and the mean age of patients with mortality was 48.57 ± 9.91. Disease duration was found as 16.37 ± 6.83 in patients with 8.16 ± 7.50 mortality in patients without mortality. When evaluated according to the disease subtype, 1980 (81.5%) of the patients who did not develop mortality were relapsing remitting, and 13 (50.0%) of the patients with mortality were RRMS patients. Average of last EDSS values; It was found as 1.89±1.07 in patients without mortality and 5.86±2.23 in patients with mortality. The most common cause of mortality was 38.5% pneumonia. This was followed by myocardial infarction, sepsis, and malignancy. The factors affecting the development of mortality were high age, long duration of the disease, having a progressive disease type and high EDSS value. Conclusion: The most common cause of mortality is infections. Advanced age, long disease duration, progressive disease type and high EDSS level are the conditions where mortality is most associated.