Although there are international guidelines on the management of anti-thrombotic therapy in patients undergoing colonoscopic polypectomy, whether clinicians and patients follow these recommendations are largely unknown.We aimed to evaluate clinicians' adherence and patients' compliance to peri-endoscopic management of antithrombotic therapy and their impact on clinical outcomes.Consecutive patients on anti-thrombotic therapy scheduled for elective colonoscopy in a tertiary referral center were prospectively recruited. Demographic data, indications and peri-procedural management of anti-thrombotic drugs, colonoscopy findings, post-polypectomy bleeding and serious cardiovascular events were systematically collected. We used Joint APAGE-APSDE Practice Guidelines 2018 and assumed clinicians should hold antithrombotic for polypectomy in all colonoscopy patients. Patients' compliance was assessed by checking whether discontinuation and resumption of anti-thrombotic drugs were in accordance with clinicians' advice.Between December 2017 and October 2019, 602 patients on anti-thrombotic drugs undergoing colonoscopy with polypectomy were recruited. 98.4%, 41.2%, and 40.0% of clinicians adhered to the guidelines for aspirin alone, clopidogrel alone, and dual antiplatelet therapy (DAPT), respectively. Adherence rates were 8.5% for warfarin and 5.2% for direct oral anti-coagulant (DOACs). Compliance to instructions for aspirin-alone, clopidogrel alone, DAPT, warfarin, and DOACs, were achieved in 74.8%, 41.2% ,0, 36.2% and 17.5% of patients, respectively. Clinicians' non-adherence to guidelines was risk factor for delayed post-polypectomy bleeding (adjusted HR: 3.54, CI: 1.46-8.58, P=0.005), and serious cardiovascular events (HR:15.63; 95%CI:1.83-133.80; P=0.012).Physicians' adherence to the guideline and patients' compliance, with the exception of aspirin, were poor and contributed to adverse clinical outcomes.