Background. Cardiac fibrosis is a risk factor leading to various cardiac diseases, and its mechanism has not been clarified. However, long noncoding RNA (lncRNA) can mediate the pathological process of cardiac fibrosis. Objective. This study is aimed at determining the pathological role of lncRNA Vgll3 in cardiac fibrosis and explore its potential mechanism. Methods. Myocardium fibroblasts (CFs) were isolated from mice and stimulated with angiotensin II (Ang-II). The expression of Vgll3 and transforming growth factor-β3 (TGF-β3) were detected by real-time fluorescence quantitative PCR (qPCR). Double luciferase reporter gene and western blot analysis (WB) were used to detect the effect of Vgll3 on TGF-β3 expression. The qPCR and WB were used to detect TGF-β3 pathway markers such as TGF-β3 and SMAD4, as well as cardiac fibrosis markers such as α-smooth muscle actin (α-SMA), fibronectin (Fn), and type I collagen (Col1). The proliferation of CFs in mice was analyzed by Cell Counting Kit-8 (CCK8) and 5-bromo-2-deoxyuracil (EdU) method. Results. Upregulation of Vgll3 promoted the expression of TGF-β3 and its downstream molecules in mouse CFs, while silencing of Vgll3 inhibited the TGF-β3 pathway. Upregulation of Vgll3 significantly promoted the activation and proliferation of mouse CFs cells. It promoted the mRNA and protein levels of α-SMA, Fn, Col1, and Col3, while silencing the expression of Vgll3 had the opposite effect. The above effects of upregulation of Vgll3 were counteracted by TGF-β3 knockdown intervention. Conclusion. Vgll3 can promote the activation and proliferation of CFs in mice by activating TGF-β3-related pathway.