Background: and Purpose Cognitive impairment (CI) is a common symptom of multiple sclerosis (MS). Although demographic and clinical factors contribute to MS-dependent CI, previous findings have been inconsistent. This study aimed to identify the cognitive domains that are impaired in MS patients, and to determine the impacts of the Expanded Disability Status Scale (EDSS) score and other clinical and demographic factors on them domains. Methods: This study enrolled 115 MS patients. Cognitive performance was assessed using the Minimal Assessment of Cognitive Function in Multiple Sclerosis (MACFIMS) battery. CI severity was assessed based on the number of impaired tasks in the MACFIMS battery, with impairment in two or more tasks defined as CI cases. Correlation analysis was used to determine whether factors including current age, age at disease onset, EDSS score, disease duration, relapse rate, and education level affect the severity of CI. Results: The scores on the Paced Auditory Serial Addition Test and Delis-Kaplan Executive Function System were the most and least affected, respectively. EDSS score (r=0.438, p<0.001), current age (r=0.393, p<0.001), and disease duration (r=0.486, p<0.001) were positively correlated with CI severity, whereas education level (r=-0.527, p<0.001) had a negative correlation with CI severity, and age at disease onset and relapse rate were not correlated with CI severity (r=0.150 and p=0.107, and r=0.052 and p=0.530, respectively). However, all variables (except EDSS score) significantly predicted CI severity in a multiple regression model (p<0.001, r=0.668). Conclusions Information processing speed and working memory were the most commonly affected cognitive domains in the present MS patients. CI severity had strong positive correlations with current age, EDSS score, and disease duration, and a negative correlation with education level. The relapse rate and age at disease onset were not correlated with CI severity.