To evaluate the potential role of serum and tissue hsa_circ_0008621 as a prognostic biomarker for CRC patients. Focused on the functional role of hsa_circ_0008621 in colorectal cancer (CRC). Serum and tissue hsa_circ_0008621 expression were quantified by qRT-PCR in 157 CRC patients, as well as 100 serums from healthy controls. Serum and tissue hsa_circ_0008621 expression was evaluated for their prognostic role in CRC patients using Kaplan-Meier curves and Multivariate Cox proportional hazards analysis. To further characterize the biological role of hsa_circ_0008621 expression in CRC, invitro hsa_circ_0008621 inhibition was performed and the effects on cellular growth, migration, invasion, apoptosis, and glycolysis were explored. Next, the downstream molecules for hsa_circ_0008621 were predicted. Hsa_circ_0008621 expression was significantly upregulated in CRC tissues and serums. Serum hsa_circ_0008621 levels were significantly up-regulated in advanced-staged samples. High serum hsa_circ_0008621 expression was associated with shorter overall survival and recurrence-free survival in CRC patients. Multivariate Cox regression analysis identified a high level of serum hsa_circ_0008621 expression as an independent prognostic factor with respect to overall survival and recurrence-free survival. Loss of function assays for hsa_circ_0008621 invitro led to a significant decrease in cell proliferation, migration, invasion, and glycolysis, but an increase in cell apoptosis. Hsa_circ_0008621 can sponge miR-532-5p, which targets SLC16A3. High level of serum hsa_circ_0008621 is associated with poor survival in CRC and promotes CRC progression, suggesting it to be a promising non-invasive prognostic biomarker and novel therapeutic target in CRC patients.