Objective: Cognitive intraindividual variability (C-IIV), a measure of an individual's fluctuations in cognitive performance, has become a topic of interest in neuropsychology due to its potential to predict cognitive dysfunction. Existing studies suggest that C-IIV may be the result of fluctuations in motivation, increased fatigue, or represent true idiosyncratic strengths and weaknesses of an individual. The following study aimed to examine the relationship between C-IIV and demographic and illness related variables known to be associated with cognitive dysfunction in Multiple Sclerosis (MS). Method: Fifty-eight individuals with MS participating in a neuropsychological research study of MS-related factors were examined. C-IIV scores were calculated by taking the standard deviation of sample-normed measures of processing speed, memory, and executive functioning. This measure of C-IIV was then correlated with demographic variables (age, education, sex, IQ) and illness-related variables (Expanded Disability Status Score (EDSS), disease duration, fatigue, and depression). Results: C-IIV did not significantly correlate with age, education, sex, EDSS, disease duration, fatigue, or depression. However, C-IIV negatively correlated with a measure of Full-Scale IQ (Shipley), R= −.31, p = .018. This relationship remained significant when controlling for years of education, R = −.30, p = .024. When Full-Scale IQ was parsed into its components, C-IIV correlated with fluid intelligence (Shipley-Abstraction), R = −.30, p = .03, but not with crystalized intelligence (Shipley-Vocabulary), R = .20, p > .10. Conclusion: This study found that C-IIV was related to intelligence, such that higher C-IIV was particularly associated with lower fluid intelligence. Lower C-IIV may be driven by well-preserved fluid IQ in MS, or both may be indicative of better brain integrity, something future work could explore.