Objective: This study aimed to investigate the expression of B7-H4 in human thyroid cancer and determine any association with patient clinicopathological parameters and survival. Methods: B7-H4 expression in 64 clinical thyroid cancer specimens was assessed with immunohistochemistry. Moreover, B7-H4 mRNA expression in 10 fresh resected specimens were evaluated by the reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemical staining of CD3 was performed to assess the number of tumor infiltrating T lymphocytes (TILs) in thyroid cancers. Results: Positive B7-H4 immunohistochemical staining was observed in 61 out of 64 (95.3%) specimens of thyroid cancer tissues. Significantly more B7-H4 mRNA copies were found in thyroid cancer tissue than that adjacent normal tissue. Moreover, B7-H4 expression in human thyroid cancer tissues was significantly correlated with patient TNM stages and extrathyroidal extension (P<0.05), being inversely correlated with the number of TILs (P<0.05). The overall survival rate of the patients with higher B7-H4 expression was significantly worse than that of the patients with lower B7-H4 expression. Conclusions: This present study suggests that high B7-H4 expression is associated with cancer progression, reduced tumor immunosurveillance and worse patient outcomes in human thyroid cancer.