Insulin-like growth factor (IGF)-I receptor (IGF-Ir) signaling is required for tumorigenicity and progression of many tumors but this pathway has not been well studied as a prognostic factor or potential therapeutic target in esophageal squamous cell carcinoma (ESCC). In this paper, the association between the expression of IGF-Ir and IGF-II ligand and prognosis was investigated immunohistochemically in 100 surgically resected ESCC. We then assessed the therapeutic effect of blocking IGF receptor signaling using dominant negative IGF-Ir (IGF-Ir/dn) in ESCC in vitro. Expression of IGF-Ir and IGF-II were detected in 60 and 50% of tumors, respectively, and were associated with invasion depth, metastasis, advanced tumor stage and recurrence. Patients with tumors expressing both IGF-Ir and IGF-II had a significantly shorter survival than those expressing either alone or neither in both single and multivariate analysis. IGF-Ir/dn suppressed proliferation and motility as well as upregulating chemotherapy-induced apoptosis through blocking ligand-induced Akt activation. We propose that detection of IGF-Ir/IGF-II in ESCC may be useful for the prediction of recurrence and poor prognosis and for selecting patients for IGF-Ir-targeted therapy. Therapeutic blockade of IGF-Ir may be a useful anticancer therapeutic for ESCC.