BACKGROUND: SERPINI1 is a protein-coding gene, which has been reported to be related to malignancies, and the encoding protein is a secreted protein. Nevertheless, the specific effect of SERPINI1 on Hepatocellular carcinoma (HCC) remains unclear. METHODS: The expression level of SERPINI1 in cancers was detected by the Gene Expression Omnibus (GEO) database, the Gene Expression Profiling Interactive Analysis (GEPIA) database and the collected serum of HCC patients. The receiver operating characteristic (ROC) curve and area under curve (AUC) were used to evaluate the diagnostic effectiveness of serum SERPINI1 and the combination of AFP and SERPINI1 for HCC. The Kaplan-Meier (KM) survival was used to evaluate the prognostic capacity of SERPINI1 for HCC in GEPIA database. Furthermore, the correlations between clinicopathological characteristics and the level of serum SERPINI1 were analyzed. Besides, we detected the expression of SERPINI1 in HepG2 by qPCR and western blot, and confirmed the biological function of SERPINI1 through MTT, EdU, wound healing and transwell invasion assay. RESULTS: The results indicated that the level of SERPINI1 was significantly increased in tissue and serum of HCC patients. ROC analysis displayed that SERPINI1 had a significantly diagnostic value for HCC, the combination of AFP and SERPINI1 gained the higher specificity and sensitivity. The KM survival curves indicated that patients with SERPINI1 overexpression had worse overall survival. Furthermore, we found the positive correlations between serum SERPINI1 level and some clinicopathological characteristics, such as tumor size, differentiation degrees and so on. In addition, in vitro experiments revealed that SERPINI1 could promote the proliferation and invasion of HCC. CONCLUSIONS: Taken together, our study demonstrates that SERPINI1, which is highly expressed in HCC and closely related to cell proliferation and invasion, may serve as a novel biomarker for diagnosis and prognosis of HCC.