Accumulating data have suggested exosome-delivered microRNAs (miRNAs) play critical role in carcinogenesis and cancer progression. However, little is known about the influence of exosomal miR-6803-5p on the development and prognosis of colorectal cancer (CRC). Levels of serum exosomal miR-6803-5p were determined by microarray analysis and verified by quantitative real-time PCR (qRT-PCR). Outcomes of overall survival (OS) and disease-free survival (DFS) of CRC patients were estimated by Kaplan-Meier analysis. We used cox regression analysis to investigate the association between exosomes-encapsulated miR-6803-5p and the clinicopathological factors of CRC patients. The exosomal miR-6803-5p was significantly increased in serum samples from patients with CRC in contrast to healthy controls. Significantly higher levels of serum exosomal miR-6803-5p were observed in CRC patients at later TNM stage or with lymph node metastasis as well as liver metastasis. Patients with elevated levels of serum exosomal miR-6803-5p had much poorer OS and DFS. Cox regression analysis revealed high levels of exosomal miR-6803-5p was associated with poor prognosis in CRC independent of other confounding factors. Thus, exosomal miR-6803-5p is a potential diagnostic and prognostic biomarker for patients with CRC.