Recent evidences highlight the crucial regulatory roles of long noncoding RNAs (lncRNA) in tumor biology. LncRNA CASC7 is a ∼9.3kb lncRNA whose function is currently unknown. The present study aimed to investigate the expression of CASC7 in patients with colorectal cancer (CRC) and its effect on CRC cells. The expression levels of CASC7, miR-21 and ING3 were estimated by reverse transcription-quantitative polymerase chain reaction (RT-PCR) or western blot in CRC tissues and CRC cell lines (SW480 and HCT-116). The relationship between miR-21 and CASC7 or ING3 was analyzed by RNA immunoprecipitation (RIP), RNA pull-down and luciferase reporter assay. In addition, the biological roles of CASC7 were examined using cell counting kit-8 assay, flow cytometry, and migration and invasion assays following the downregulation or upregulation of CASC7 by small interfering RNA or pcDNA-CASC7, respectively. In this study, CASC7 expression was significantly decreased in CRC tissues and CRC cell lines. Further functional experiments suggested that CASC7 overexpression could inhibit cell viability, migration and invasion, and promote apoptosis in CRC cells. CASC7 and ING3 were both a target of miR-21 in CRC cells, and CASC7 could control ING3 expression by regulating miR-21. Moreover, we have found that CASC7 inhibited colon cancer cell proliferation and migration via miR-21/ING3 axis. These observations suggested that CASC7 played an important role in CRC pathogenesis and may be considered as a novel diagnostic marker of CRC.