The numerical study of the impact of thermal radiation, chemical reaction, and heat source on MHD Casson fluid flow over a nonlinear inclined stretching surface with velocity slip in a Forchheimer porous medium is presented in this paper. The controlling equations are converted into nonlinear ODE's with appropriate similarity variables. Numerical solutions of the nonlinear ODE’s are solved by the Runge-Kutta method along with the shooting technique with MATLAB. It is vital to investigate the flow of Casson fluids (such drilling muds, clay coatings, various suspensions and certain lubricating oils, thermoplastic melts, and a variety of colloids) in the incidence of heat transfer in order to optimize the preparation of toffee, chocolate, and other delicacies. Numerical findings were given via graphs and tables for various intervals of the physical variables involved for velocity, temperature, and concentration profiles in addition to this, the coefficient of skin friction, Nusselt number, and local Sherwood number are also discussed. It is inferred from the graphs that the temperature of the plate decreases with increasing the values of the radiation parameter and Forchheimer porous medium parameter. The concentration is decreased in the presence of chemical reaction and Schmidt number. To ensure the validity of our findings, we compared them to previously published work and found significant agreement.