Background: The recommendation to administer extended-duration (28 days) venous thromboembolic events (VTE) prophylaxis with low molecular weight heparin in patients undergoing abdominal and pelvic surgery for cancer has not been widely implemented mainly because most studies focus on asymptomatic events with unknown clinical significance. The objective of this study was to determine the post-hospital discharge VTE incidence in these patients who do not receive post-hospital discharge prophylaxis. Methods: Prospective cohort study of patients undergoing abdominal and pelvic operations for cancer within the gastrointestinal tract, hepatobiliary (HPB) system or gynecological organs, with surgery lasting > 1 hour, post-operative stay < 28 days, and not undergoing anticoagulant therapy. Patients were evaluated at 1, 3 and 6 months from index operation for the presence of VTE by means of a screening ultrasound at 28 days and a questionnaire at each follow-up. The proportion with 95% confidence interval (CI) of VTE was calculated. Multivariable logistical regression was performed. Results: Of 284 patients, there were 79 (28%) colorectal, 97 (35%) HPB and 100 (35%) gynecology. All patients received pre- and post-operative in-patient prophylaxis. The proportion of VTE at 6 months was 7%, 95% CI 4.4-10.7 (20 events). Most events occurred between 3-6 months, 4.6%, 95% CI 2.46 – 7.7. Only one event occurred at one month after surgery (0.35%, 95% CI 0.06-1.97). 50% of the cohort had screening ultrasound, all of which were negative. Events were evenly distributed according to the type of surgery. The proportion of patients who died was 6.6%, 95% CI 3.5 – 9.4 (17 patients, 2 of which had a VTE-related death). In the multivariable analysis, post-operative chemotherapy was significantly associated with VTE, odds ratio (OR) 2.74, 95% CI 1.07-6.99. Caprini score was also associated with VTE but was not significant when included in the multivariable analysis, OR 1.19, 95% CI 0.99-1.42. Conclusions: Incidence of VTE following abdominal cancer surgery is low. Most events occur between 3-6 months from surgery. Post-operative chemotherapy is significantly associated with post-hospital discharge VTE.