Circular RNAs (circRNAs) are a class of non-coding RNAs with a loop structure; however, their functions remain largely unknown. Growing evidence suggests that circRNAs play a pivotal role in the progression of malignant diseases. However, the expression profiles and function of circRNAs in hepatocellular carcinoma (HCC) remain unclear. We investigated the expression of microtubule-associated serine/threonine kinase 1 (MAST1) circRNA (circMAST1) in HCC and healthy tissues using bioinformatics, quantitative real-time PCR (qRT-PCR), and fluorescence in situ hybridization. Luciferase reporter assays were performed to assess the interaction between circMAST1 and miR-1299. Proliferation assays, colony formation assays, flow cytometry, transwell assays, and western blotting were also performed. A mouse xenograft model was also used to determine the effect of circMAST1 on HCC growth in vivo. CircMAST1 was upregulated in HCC tissues and cell lines; silencing via small interfering RNA inhibited migration, invasion, and proliferation of HCC cell lines in vitro as well as tumor growth in vivo. Furthermore, the expression of circMAST1 was positively correlated with catenin delta-1 (CTNND1) and negatively correlated with microRNA (miR)-1299 in HCC clinical samples. Importantly, circMAST1 sponged miR-1299 to stabilize the expression of CTNND1 and promoted tumorigenic features in HCC cell lines. We found that circMAST1 may serve as a novel biomarker for HCC. Moreover, circMAST1 elicits HCC progression by sponging miRNA-1299 and stabilizing CTNND1. Our data provide potential options for therapeutic targets in patients with HCC.