Circular RNAs (circRNAs) have been recently identified as widespread and diverse endogenous noncoding RNAs that may harbor vital functions in humans. However, the role of circRNAs in the process of tumorigenesis and development of colorectal cancer (CRC) remains hitherto vague. In this study, we investigated the expression level of circ_0002138 in 35 paired CRC tissues by quantitative real-time polymerase chain reaction (qRT-PCR) and found that circ_0002138 was stably down-regulated in CRC tissues compared to paired adjacent normal tissues (P < 0.001). Fisher's exact test was further conducted to analyze the relationship between circ_0002138 expression level and clinico pathological factors of CRC patients. Circ_0002138 expression was significantly correlated with age. To evaluate the diagnostic value of circ_0002138, a receiver operating characteristic (ROC) curve was used and the area under the ROC curve was 0.7249. Additionally, functional analysis demonstrated that circ_0002138 significantly inhibited CRC cell proliferation in vitro. Overall, our data suggest that circ_0002138 may become a novel potential biomarker for diagnosis and treatment target of CRC.