iASPP is shown to be elevated in several cancers. However, the role of iASPP in head and neck squamous cell carcinoma (HNSCC) remains unknown. We have investigated iASPP expression in HNSCC tissue and cell lines and evaluated its prognostic significance in HNSCC. The expression of iASPP in 109 primary HNSCC tissue specimens was examined by immunohistochemistry and its association with clinicopathological parameters and prognosis was analyzed. Additionally, expression status of iASPP in 16 paired HNSCC tissues and 7 HNSCC cell lines was evaluated by quantitative real-time PCR (qPCR) and immunoblotting. The protein and mRNA expression of iASPP were increased in HNSCC tissues and cell lines. Immunohistochemical staining indicated iASPP was detected in both cytoplasm and nucleus. Importantly, overexpression of cytoplasmic and nuclear iASPP was significantly associated with T classification (p = 0.002 and p = 0.033, respectively), clinical stage (p < 0.001 and p = 0.004), lymph node metastasis (p = 0.001 and p < 0.001), and recurrence (both p < 0.001). Survival analysis demonstrated high iASPP expression significantly correlated with shorter disease-free survival (DFS) (both p < 0.001 for cytoplasmic and nuclear expression) and overall survival (OS) (both p < 0.001 for cytoplasmic and nuclear expression). Multivariate analysis revealed that cytoplasmic iASPP was the only independent prognostic factor for HNSCC patients. iASPP expression is elevated in HNSCC tissues and cell lines, which suggests iASPP may contribute to the malignant progression of HNSCC, and serves as a novel prognostic marker and a potential therapeutic target in HNSCC.