Background and Objective: syndecan-1, a member of a family of cell-surface proteoglycans, is known to bind with cell-to-cell and cells-to-interstitial matrix. The aim of the present study was to evaluate the syndecan-1 expression in erosive lichen planus, epithelial dysplasia and oral squamous cell carcinoma (OSCC) . Materials and methods: A total of 10 erosive lichen planus,5 epithelial dysplasia and 20 OSCC were prepared for immunohistochemical staining of syndecan-1.The results were scored mild, moderate and severe based on the predominant staining intensity and characterization of membranous and cytoplasmic membrane staining. Results:The results of staining intensity in OSCC in most of samples were mild (50%) or moderate (45%). The lichen planus in most cases had severe (50%) or moderate (40%) staining. As well as, in the dysplasia cases4 samples(80%) had severe staining and one case(20%) showed moderate staining and the difference was statistically significant (p = 0.03).in more cases of OSCC(90%) both membranous and cytoplasmic expression was observed. Membranous staining was observed in 8 (80%) cases of lichen planus. The membranous staining was observed in all samples (100%) of dysplasia, and the difference was statistically significant(p=0.00). Conclusion:The expression of syndecan-1 in OSCC was significantly less than lichen planus and dysplasia. The reduction of the expression of syndecan-1 in Lichen Planus (similar to what was seen in OSCC) may be a sign of a potential pre-malignant of lesion, but this requires further investigation.