<p>This study investigates the haemodynamic characteristics of a two-layered MHD Jeffrey fluid model in a diverging narrow arterial channel featuring multiple stenoses and a porous layer, adhering to a no-slip boundary condition. The central region, distinguished by plasma rich in RBCs, is modelled as a Jeffrey fluid, while the peripheral region is considered a Newtonian fluid to depict the stratified structure of blood in small vessels. This configuration is relevant for comprehending pathological blood flow in conditions such as atherosclerosis and vascular constriction. An analytical approach is employed to derive accurate formulations for velocity, effective viscosity, and haematocrit. The derived expressions are assessed utilising MATHEMATICA. The results demonstrate that effective viscosity increases with the Jeffrey parameter (an increase of 22% as λ₁ changes from 0.1 to 0.5) and the magnetic parameter, whereas it decreases with the Darcy number and the wall exponent. The core haematocrit diminishes by roughly 19% with increasing magnetic field intensity, attributed to the redistribution of RBCs towards vessel walls, whereas the mean haematocrit increases with channel width and viscoelasticity. The model includes critical physiological phenomena like the Fahraeus–Lindqvist effect, confirming consistency with recognised clinical observations. The study's novelty lies in its comprehensive analytical investigation of Jeffrey fluid dynamics, magnetohydrodynamic effects, porosity, and complex arterial geometry elements rarely examined together in previous research. These findings offer substantial insights into blood flow regulation in stenosed arteries and have practical implications for biomedical applications, such as magnetic drug targeting, hyperthermia therapy, and perfusion design in porous vascular networks.</p>