Over the past several years, considerable focus has been placed on the need for 'biomarkers'. However, traditional biomarkers, such as CEA or CA19-9, for gastrointestinal cancer do not provide sufficient sensitivity and specificity for diagnosing cancer. Moreover, these biomarkers cannot provide information regarding the individual variability of patients. Recently, extracellular vesicles (EVs) and extracellular microRNA (miRNA) have shown potential in cancer diagnosis because tumor cells have been shown to release EVs and miRNAs, which mirror their cellular origin, into circulation. Therefore, detection of tumor-specific EVs and extracellular miRNA in body fluids from cancer patients could serve as a non-invasive liquid biopsy for cancer diagnosis and monitoring. This review explores the potential contribution of liquid biopsy using EVs and extracellular miRNA to diagnosis and monitor cancer, including an assessment of prognosis and early detection of disease recurrence in patients with cancer.