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The effects of red blood cell (RBC) motion on thrombus formation have been extensively studied in microvessels with diameters on the order of 100 μm. However, the influence of RBC motion in larger vessels remains poorly understood. In this study, the kinematic effects of RBCs on blood coagulation in medium-sized vessels (~1 mm in diameter) were investigated using two-dimensional particle-based simulations. Blood was modeled as a two-phase system consisting of plasma and deformable RBCs. RBC dynamics were simulated by coupling membrane elastic deformation with the surrounding fluid flow. Simultaneously, reaction–advection–diffusion equations governing the concentrations of coagulation factors in plasma were solved using a previously reported intrinsic coagulation model. A parallel-plate flow channel with a width of 500 μm and periodic boundary conditions was employed. The simulations showed that increasing the shear rate from 0.4 s⁻¹ to 400 s⁻¹ enhanced the shear-induced diffusive migration of RBCs in the lateral direction. As a result, the apparent diffusion coefficient of coagulation factors increased, which delayed the onset of excessive thrombin generation at the procoagulant wall. At the same time, enhanced transport promoted lateral spreading of the high-thrombin region and increased the propagation velocity of the thrombin wave. These findings suggest that shear-induced diffusive RBC migration significantly enhances coagulation factor transport and thereby modulates blood coagulation dynamics in medium-sized vessels.