Abstract: Hepatocellular carcinoma (HCC) is the most common primary hepatic malign-ancy in clinic. The prognosis of patients remains extremely poor because of the high malignancy and easy recurrence and metastasis of HCC. In recent years, the roles of platelets in promoting the malignant progression of HCC have increasingly attracted much attention. It is known that platelets could promote HCC cells proliferation and invasion through tumor microenvironment. On the other hand, platelets are capable to promote HCC cells distant metastasis by facilitating tumor cells evasion of immune surveillance. Besides, the platelet-derived growth factors and proangiogenic factors are also involved in the proliferation, invasiveness, and neovascularization of HCC. In addition, patients with HCC normally have a background of cirrhosis, and it is still controversial that whether the thrombocytopenia by portal hypertension and hypersplenism can promote the malignant progress of HCC. In view of this, the diagnostic and prognostic value of platelet levels, as well as platelet-associated scores in HCC have increasingly become research focus. The authors elaborate the detailed mechanisms of platelets in malignant progression of HCC, and discuss the recent research progress of platelets as effective diagnostic or prognostic tools for the assessment of HCC, which is of great importance to optimize the current treatment regimen and explore novel therapeutic strategies against HCC.