Background: Semaphorin-3A (Sema3A), as a secreted semaphorin, is an immune modulator molecule participating in the pathogenesis of autoimmune diseases. MicroRNAs (miRNAs) modulate the target-gene expression at the post-transcriptional level. It has been proposed that miRNAs may be crucial to the modulation of the function of semaphorins. Previous findings have proven that miR-497-5p is upregulated and Sema3A is downregulated in some autoimmune disorders. Thus, we aimed to examine the presence of any correlation between Sema3A and miR-497-5p in peripheral blood mononuclear cells (PBMCs). Methods: PBMCs were cultured and transfected with miR-497-5p mimic using the X-tremeGENE™ reagent. The expression level of Sema3A was assessed after 48 hours in supernatants and cells via the enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively. Cell viability was evaluated using the methylthiazol tetrazolium assay. All the experiments were done in triplicate, and the statistical analyses were performed with SPSS, version 20. P values equal to or less than 0.05 were considered significant.Results: We observed downregulation of the Sema3A gene (P=0.0001) and its secretion (P=0.032) in the PBMCs through miR-497-5p transfection. Moreover, transfection with miR-497-5p mimic and downregulation of Sema3A did not affect the viability of the PBMCs (P=0.061).Conclusion: Based on the obtained results, we suggest that miR-497-5p has a high suppressive effect on Sema3A expression and both Sema3A and miR-497-5p can be considered critical targets for further studies on future therapeutic attempts for the treatment of autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.