Background Conjunctival intraepithelial neoplasia (CIN) is a preinvasive lesion of the ocular surface epithelium that can progress to squamous cell carcinoma (SCC), which has the potential to invade the nearby tissues, leading to visual loss. Unfortunately, the exact mechanisms of CIN and SCC pathogenesis, remain largely unknown. Cytokeratin 17 (CK17) functions specially among keratins as an oncoprotein which has been overexpressed in several cancers. To date, studies about the expression pattern of CK17 in CIN and SCC are limited. Aim The aims were to examine the immunohistochemical expression of CK17 in different conjunctival specimens including morphologically normal conjunctiva, pterygium, CIN, and SCC, and correlate CK17 expression with the available clinicopathological features of CIN and SCC specimens. Materials and methods The authors immunohistochemically investigated CK17 expression in 73 conjunctival specimens (40 CIN, 15 SCC, 10 pterygium, and eight morphologically normal conjunctiva). Results Overexpression of CK17 was detected in CIN and SCC specimens. On the contrary, limited basal expression of CK17 was noted in pterygium specimens and most of the morphologically normal conjunctiva. Significant higher mean of CK17 expression was found in CIN than morphologically normal conjunctiva and pterygium specimens. Moreover, the mean of CK17 expression was significantly higher in SCC specimens than CIN. Insignificant difference was detected between CK17 expression and all the clinicopathological features in CIN and SCC. Conclusion The authors can suggest that CK17 plays a role in the pathogenesis of CIN and SCC, with a possible role of CK17 in differentiation between benign and malignant conjunctival lesions.