This systematic review study aimed to evaluate the impact of TES on cognitive dysfunction in MS patients, aiming to consolidate current knowledge and explore its clinical applicability. A PRISMA-compliant search of MEDLINE, Scopus, and EMBASE identified randomized controlled trials (RCTs) and quasi-experimental studies assessing TES’s impact on cognitive outcomes in MS. Data from nine studies were pooled using random-effects models, with subgroup analyses by stimulation type. Meta-analysis revealed a small-to-moderate pooled effect of TES on cognitive function (standardized mean difference [SMD] = 0.62, 95% CI: 0.36–0.88, p < 0.001), though substantial heterogeneity was observed (I2 = 87.82%). Subgroup analysis showed tDCS improved cognitive outcomes (SMD = 0.32, p = 0.04), while tACS demonstrated a larger but non-significant effect (SMD = 1.39, p = 0.16). TES was generally safe, with transient side effects (e.g. scalp discomfort) reported. TES shows promise as an effective and safe intervention for cognitive dysfunction in MS patients. While improvements were observed in various cognitive domains, outcome variability underscores the need for further research to refine stimulation protocols.