BACKGROUND Pulmonary embolism (PE) is a serious and preventable complication after surgery. Blood transfusion is a common event during surgery. The aim of the present study was to identify whether intra-operative blood product transfusions increase the risk of symptomatic post-operative PE. METHODS A retrospective, single-center case-control study at Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University between 1 January 2013 and 31 December 2016 was performed. Adult hospitalized patients with confirmed symptomatic PE after surgery were defined as case group. Each patient was matched with two adult patients without symptomatic PE who underwent the same procedure on the same day or within one week. Perioperative data especially detailed blood transfusion was collected. Forward stepwise logistic regression analysis was performed. RESULTS During the study period, altogether 188,512 procedures were included, and postoperative PE were confirmed in 40 (0.02%) patients. Twelve (30.0%) case patients and 16 (20.0%) control patients received intra-operative blood transfusion. Intra-operative blood transfusion was revealed as a significant predictor for symptomatic post-operative PE (OR 80.669, 95% CI: 3.312-1,964.641, P=0.007), along with female sex (OR 86.921, 95% CI: 4.242-1,781.124, P=0.004), older age (OR 1.078, 95% CI: 1.005-1.156, P=0.035), longer length of stay before surgery (OR 1.124, 95% CI: 1.040-1.214, P=0.003) and longer operation time (OR 1.013, 95% CI: 1.002-1.025, P=0.024). CONCLUSIONS Intra-operative blood transfusion was associated with an increased risk of symptomatic post-operative PE. PE prophylaxis and selective screening should be considered in patients who had received intra-operative blood transfusion, especially in female patients.