Cardiac fibrosis is a common pathological condition that contributes to the progression of many cardiac diseases. Circular RNAs (circRNAs) are emerging as new regulators of cardiac fibrosis. However, the expression and function of circRNAs in cardiac fibrosis remain largely unknown. The present study aims to investigate the circRNA expression profile and identify the roles of circRNAs in cardiac fibrosis. Transforming growth factor-β1 (TGF-β1) was used to establish an in vitro model of cardiac fibrosis in cardiac fibroblasts. CircRNA sequencing revealed that a total of 283 circRNAs were aberrantly expressed in fibrotic cardiac fibroblasts, with 79 upregulated and 204 downregulated. The expression changes of randomly selected circRNAs were validated by real-time PCR. A circRNA-based competing endogenous RNA network 1755 nodes and 30394 edges was established, and module analysis was conducted using the plug-in MCODE. KEGG pathway enrichment analysis was performed for mRNAs involved in the top three enriched modules. The results showed that these mRNAs were enriched in cardiac fibrosis-related signalling pathways, including the ‘TGF-beta signaling pathway’, ‘MAPK signaling pathway’, ‘AMPK signaling pathway’, and ‘PI3K-Akt signaling pathway’. The predicted ceRNAs and bioinformatics analysis revealed the potential role of circRNAs in cardiac fibrosis, which would provide useful information for understanding the mechanism and finding effective prevention and treatment targets for cardiac fibrosis.