Objective: Examine if outcomes and complication rates for free flaps vary when postoperative aspirin and LMWH are used as pharmacologic thromboprophylaxis compared with only low dose heparin. Background: Many protocols exist to prevent thrombosis after free–tissue transfer. Many surgeons advocate using low dose heparin and aspirin or other antiplatelet agents in the postoperative period, but little objective evidence supports this practice. This study evaluates the rate of microvascular thrombosis in patients undergoing free–tissue transfer treated with or without antiplatelet agents. Methods: All consecutive free flaps for lower limb reconstruction from 2011–2017 at a single centre were reviewed retrospectively using a maintained database. Patients were divided in 2 groups based on postoperative anticoagulation administration. In group A, 5000 units of LMWH per day for 5 days with 325 mg of aspirin was administered daily for 30 days postoperatively. In group B, 5000 units of LMWH per day for 5 days. Patient demographics, diagnosis, procedure type were recorded. Outcome variables included microvascular thrombosis, partial or total flap loss, hematoma, bleeding, deep venous thrombosis (DVT), pulmonary embolism, and death. Results: 634 patients underwent microvascular free flaps for lower limb reconstruction. 254 flaps (group A) received postoperative LMWH & aspirin therapy; 380 flaps (group B) received LMWH therapy only. Both groups were statistically similar in their composition. No statistically significant difference was noted between the 2 groups when comparing outcome variables including microvascular thrombosis, partial or total flap loss, hematoma, bleeding, DVT, pulmonary embolism, and death. Conclusions: Postoperative aspirin administration has no statistically significant effect on the incidence of free flap complications, including bleeding, thromboembolism, and flap loss. We conclude LMWH with or without aspirin therapy demonstrates equivalent outcomes when used as postoperative anticoagulation in free flap reconstruction.