Introduction: An impaired sense of smell has a remarkable impact on the quality of life. It is seen in a variety of neurodegenerative diseases such as Parkinson disease. In this study, we assessed the olfactory function in patients with Multiple Sclerosis (MS) by Sniff Magnitude Test (SMT). 
Methods: A cross-sectional study was conducted on 48 patients with MS. A questionnaire, including demographic and clinical variables, was completed for each patient. The SMT was used for the evaluation of olfactory function. 
Results: Olfactory dysfunction was found in 14.6% of patients (8.3% hyposmia and 6.3% anosmia). Older age, longer disease duration, higher hospital admission rate, lower mini-mental status examination score, and secondary progressive course of MS were significantly related to olfactory dysfunction. 
Conclusion: Secondary progressive MS and markers of advanced disease toward neurodegenerative phase (including older age, longer disease duration, and lower cognitive function) can be associated with olfactory dysfunction in MS patients.