The effect of these variants on coagulation factor levels remains similarly uncertain.<h4>Objectives</h4>To test the association of the C677T and A1298C missense variants in MTHFR with risk of venous thromboembolism (VTE), cardioembolic stroke (CES), and circulating coagulation cascade protein levels.<h4>Patients/methods</h4>We analyzed genetic associations of MTHFR missense variants with VTE (81,190 cases and 1,419,671 controls), CES (10,804 cases and 1,234,808 controls), and circulating levels of coagulation cascade proteins from the deCODE (n = 35,559) and UK Biobank (n = 46,218) cohorts. This evidence concerns the gene MTHFR and cardioembolic stroke.