Pituitary tumor transforming gene-1 (PTTG1) has been suggested to serve as an oncogene in several types of human tumors, but little is known about the biological function of PTTG1 in colorectal cancer. PTTG1 mRNA and protein expressions in colorectal cancer tissues and cell lines were measured by qRT-PCR, western blot or immunohistochemistry. The association between PTTG1 protein expression and clinicopathological features was analyzed. The function of PTTG1 on colorectal cancer cell proliferation and metastasis were explored through MTT, colony formation, migration and invasion assays. In our results, PTTG1 mRNA and protein expressions were increased in colorectal cancer tissues and cell lines compared with normal colonic tissues and colon epithelial cell line. PTTG1 overexpression positively associated with clinical stage, T classification, N classification, M classification and differentiation. The univariate and multivariate analyses suggested PTTG1 overexpression was an independent poor prognostic factor for colorectal cancer patients. The in vitro experiments showed knocking down PTTG1 inhibited colorectal cancer growth and metastasis. In conclusion, PTTG1 is an independent prognostic factor and acts as an oncogene in colorectal cancer.