This study investigates the influence of thermal radiation and chemical reaction on magnetohydrodynamic (MHD) mixedconvection flow of a Casson fluid over a nonlinear stretching sheet embedded in a porous medium. The non-Newtonian behavior of theCasson fluid, combined with the effects of buoyancy forces, magnetic field, and porous medium resistance, is analyzed under nonlinearstretching conditions. The governing partial differential equations (PDEs) are transformed into a system of nonlinear ordinary differentialequations (ODEs) using suitable similarity transformations. The resulting equations are solved numerically using the Runge-Kutta-Fehlberg(RKF) method with shooting technique. The impacts of key parameters such as the Casson fluid parameter, magnetic field strength, thermalradiation, chemical reaction rate, porosity, and nonlinear stretching exponent on velocity, temperature, and concentration profiles arediscussed in detail. Additionally, the skin friction coefficient, Nusselt number, and Sherwood number are evaluated to assess the flowdynamics, heat transfer, and mass transfer characteristics. The results reveal that thermal radiation enhances temperature distribution whilechemical reaction significantly alters concentration profiles. The findings provide valuable insights for industrial and engineeringapplications involving non-Newtonian fluid flows, thermal processing, and mass transfer control.Keywords: Casson fluid, MHD, mixed convection, thermal radiation, chemical reaction, porous medium, nonlinear stretching sheet