<p>The study of non-Newtonian dusty fluids is important due to their applications in cooling systems, nuclear reactors, polymer processing, and particulate transport; however, unsteady two-phase Casson dusty fluid flow in porous channels under the combined effects of Newtonian heating, thermal radiation, and mass diffusion has received limited attention. Motivated by this gap, the present work investigates an unsteady magnetohydrodynamic two-phase flow of a Casson dusty fluid confined between parallel plates embedded in a porous medium. The governing nonlinear partial differential equations for the fluid and dust phases, along with the energy and concentration equations, are solved using the Poincaré–Lighthill perturbation technique. The influences of magnetic field strength, porous medium resistance, Casson parameter, thermal radiation, chemical reaction, and mass diffusion on velocity, temperature, and concentration distributions are analyzed through graphical and numerical results. In addition, important engineering quantities such as the skin friction coefficient, Nusselt number, and Sherwood number are evaluated. The results show that magnetic field and dusty fluid parameters suppress fluid motion, while thermal radiation and buoyancy effects enhance velocity and temperature, whereas chemical reaction significantly reduces concentration. These findings provide useful insight for thermal and mass transport applications involving non-Newtonian two-phase flows in porous media.</p>