Casein kinase 1 is a group of ubiquitous serine/threonine kinases that are involved in normal cellular functions and several pathological conditions, such as DNA repair, cell cycle progression, cytokinesis, differentiation, and apoptosis. Recent studies have indicated that casein kinase 1-epsilon (CK1) and casein kinase 1-delta (CK1) expression has a role in human cancers. We investigated the associations between CK1 and CK1 expression and the clinical parameters of oral cancer using immunohistochemical study methods on oral squamous cell carcinoma specimens. The results of our immunohistochemical analysis showed that the loss of CK1 expression was greatly associated with a poor four-year survival rate in oral cancer patients (p = 0.002). A Kaplan-Meier analysis showed that patients who had a loss of CK1 expression had a considerably poorer overall survival rate than patients who had positive CK1 expressions (p = 0.022). A univariate analysis revealed that patients who had a loss of CK1 expression had considerably poorer overall survival (OS) than patients who had positive expression (p = 0.024, hazard ratio (HR) = 1.7). In conclusion, our data indicated that the loss of cytoplasmic CK1 expression is greatly associated with poor survival and might be an adverse survival factor.