Colorectal cancer (CRC) is a common malignant tumor with a poor prognosis. However, its pathogenesis has not been fully elucidated, accounting for poor overall survival. Circular RNA (circRNA) is a class of noncoding RNAs discovered many years ago. Only recently have they been re-evaluated for their important roles in the regulation of gene expression. Studies have confirmed that circRNAs have important biological functions in a variety of malignant tumors. This study aimed to characterize one circRNA derived from the MBOAT2 gene and termed it circMBOAT2, which has been reported to promote prostate cancer progression. CircMBOAT2 is highly expressed in both CRC tissues and serum samples, and has a correlation with tumor stage. The receiver-operating characteristic curves suggested that circMBOAT2 acted as a novel diagnostic tumor marker in CRC. Univariate and multivariate analyses showed that the levels of circMBOAT2 in tissues were independent prognostic markers of CRC. Further functional studies revealed that circMBOAT2 served as a microRNA (miRNA) sponge of miR-519d-3p and promoted the proliferation, migration, and invasion of CRC cells. Also, circMBOAT2 regulated cell proliferation and migration by competitively binding to miR-519d-3p and targeting troponin-associated protein (TROAP) in CRC cells. These results suggested that circMBOAT2 might be a novel potential biomarker of CRC.