Long noncoding RNAs (lncRNAs) are involved in the progression of various cancers, including hepatocellular carcinoma (HCC). However, the biological functions of lncRNA small ubiquitin-like modifier 1 pseudogene 3 (SUMO1P3) and the underlying mechanisms remain unclear. In this study, we revealed that SUMO1P3 expression was enhanced in HCC tissues and cell lines, positively associating with tumor size and number, poor differentiation, lymphatic and distant metastasis, TNM stage, and poor prognosis in HCC patients. In vitro assays showed that SUMO1P3 depletion reduced HCC cell viability and proliferation by hindering cyclin D1 expression and Akt phosphorylation. SUMO1P3 knockdown induced HCC cell apoptosis, as indicated by increased Bax and cleaved caspase-3 expression and the decreased Bcl-2 level. SUMO1P3 silencing suppressed HCC cell migration and invasion by increasing epithelial marker E-cadherin expression and decreasing mesenchymal marker vimentin expression, as well as reducing matrix metalloproteinase (MMP)-2 and MMP-9 levels. Consistently, SUMO1P3 depletion in HCC cells retarded tumor growth and lung metastasis in vivo. Overall, these results supported the applicability of SUMO1P3 as a useful predictor of HCC prognosis and a potential therapeutic target for HCC patients.