Growing evidence suggests multiple pathophysiological mechanisms linking red blood cells (RBC) transfusions to thrombosis. This study examined blood donor, component, and recipient factors which may be associated with thromboembolic outcomes following RBC transfusion. We utilized the Recipient Epidemiology Donor Evaluation Study-III (REDS-III) database on patients transfused in 12 hospitals between 2013-2016. Stratified Cox proportional hazards regression models with time-dependent exposures were used to examine associations of donor and component modification characteristics on venous thromboembolism (VTE) in patients transfused RBC units. 59,603 patients were transfused 229,500 RBC units during 79,298 hospitalizations with post-transfusion VTE occurring in 1869 (2.4%) of patients. In adjusted regression analyses, a per RBC-unit risk of VTE was present for gamma irradiation (HR = 1.03; 95% CI: 1.02-1.03), female donor sex (HR = 1.01; 95% CI: 1.00-1.01), storage duration greater than 5 weeks (HR = 1.01; 95% CI: 1.01-1.02), AS-1 storage solution (HR = 1.01; 95% CI: 1.00-1.01), and apheresis-derived collections (HR = 1.01; 95% CI: 1.01-1.02). Among recipient factors, male sex (HR = 1.03; 95% CI: 1.02-1.04), pre-transfusion hemoglobin level (HR = 0.94; 95% CI: 0.94-0.94), body mass index strata (HR = 1.11; 95% CI: 1.08-1.14), and principal diagnoses including malignancy (HR = 1.13; 95% CI: 1.10-1.16), cardiac arrest (HR = 1.38; 95% CI:1.07-1.77) and hip fracture (HR = 1.59; 95% CI:1.53-1.66) were associated with VTE in adjusted analyses. We identified several donor, component, and recipient-specific factors associated with VTE in transfused hospitalized adult patients. In adjusted models, the dose-dependent associations of donor and component-specific factors with VTE were modest and unlikely to be clinically significant in the majority of transfused patients. Additional mechanistic and clinical studies linking blood donor and component factors with thrombotic outcomes are needed.