Background <p>Multiple Sclerosis (MS) is an immunological disorder that progressively leads to neurological dysfunction. Dysregulated microRNA expression, particularly miR-155, has been implicated in MS pathogenesis. Dicer, an enzyme responsible for processing precursor microRNAs into their mature forms, is also dysregulated in various conditions, including MS.</p> Objectives <p>This study aimed to assess plasma expression levels of miR-155 and Dicer mRNA in MS patients compared to healthy individuals and evaluate their diagnostic value and clinical significance.</p> Methods <p>We analyzed plasma samples from twenty untreated MS patients, 20 MS patients receiving IFNβ1a therapy, and twenty healthy controls. Quantitative real-time PCR was used to quantify miR-155 and Dicer mRNA levels.</p> Results <p>MiR-155 was significantly higher in untreated MS patients compared to both healthy controls and IFNβ1a-treated group (<i>p</i> &lt; 0.001). MiR-155 correlated positively with the Expanded Disability Status Scale (EDSS) (<i>r</i> = 0.683, <i>p</i> &lt; 0.001). Conversely, plasma Dicer mRNA levels didn’t differ significantly between untreated MS patients and controls. However, Dicer mRNA expression was significantly elevated in the IFNβ1a-treated patients compared to both untreated MS patients (<i>p</i> &lt; 0.001) and healthy controls (<i>p</i> = 0.001). </p> Conclusions <p>Our findings suggest that miR-155 may serve as a promising biomarker for MS diagnosis and disease severity. While Dicer mRNA expression showed limited diagnostic utility, its upregulation in IFNβ1a-treated patients suggests a potential role in monitoring disease progression and treatment response.</p>