<p>This study investigates the three-dimensional magnetohydrodynamic (MHD) flow and heat transfer of a Casson non-Newtonian fluid over an exponentially stretching sheet a configuration that better reflects practical processes such as polymer extrusion and coating flows, yet remains relatively unexplored in the literature. The Casson fluid model, which captures shear-thinning and yield-stress behavior, is systematically introduced and used to formulate the governing boundary layer equations incorporating magnetic field effects. Using similarity transformations, the partial differential equations are reduced to a coupled system of nonlinear ordinary differential equations. These are solved numerically using the Hermite wavelet collocation method, chosen for its high accuracy and computational efficiency. A detailed parametric analysis examines the impact of the magnetic field strength, Casson fluid parameter, Prandtl number, and exponential stretching rate on velocity and temperature profiles. Results show that a stronger magnetic field significantly suppresses flow velocities due to Lorentz force effects and increases thermal boundary layer thickness, while the Casson parameter reduces the velocity and elevates the temperature distribution near the sheet. The exponential stretching enhances heat transfer, as reflected in the local Nusselt number variation. These findings advance the understanding of heat and momentum transfer in three-dimensional MHD flows of yield-stress fluids and demonstrate the effectiveness of wavelet-based numerical techniques for complex boundary layer problems.</p>