Functional magnetic resonance imaging (fMRI) is critical in assessing cognitive functions and reserves in neurological disorders. This chapter specifically explores fMRI’s application in evaluating patients with drug-resistant epilepsy (DRE), where the preservation of memory is as essential as achieving surgical success. While used to assess memory functions, the conventional Wada test is invasive and often less reliable, leading to a shift toward fMRI. This noninvasive technique facilitates the precise localization of memory-related brain regions and provides valuable insights into postsurgical outcomes. We highlight the advantages of fMRI over traditional methods, underscoring its significance for predicting functional reserve and cognitive outcomes in DRE patients, particularly those with mesial temporal lobe epilepsy. Ultimately, fMRI advances presurgical evaluation, optimizing cognitive preservation in epilepsy treatment.