Oral cavity squamous cell carcinoma (OSCC) is a devastating disease that accounts for 3% of all cancer cases diagnosed annually. OSCC is usually diagnosed at advanced clinical stages, resulting in poor outcomes. To identify effective biomarkers for improved OSCC diagnosis and/or management, we simultaneously analyzed the OSCC cell secretome and tissue transcriptome. Among the 19 candidates isolated, guanylate-binding protein 1 (GBP1) was selected for further validation using serum samples from OSCC patients and healthy controls. Notably, the serum level of GBP1 was higher in OSCC patients, compared to that in healthy controls. Immunohistochemical analysis further revealed GBP1 overexpression in OSCC tissues, compared with adjacent noncancerous epithelia. Importantly, the higher GBP1 level in OSCC tissue was associated with higher overall pathological stage, positive perineural invasion, and poorer prognosis. Moreover, GBP1 modulated the migration and invasion of OSCC cells in vitro. Our results collectively indicate that integrated analysis of the cancer secretome and transcriptome is a feasible strategy for the efficient identification of novel OSCC markers.