This study presents a numerical analysis of steady boundary layer flow of a Casson nanofluid over a stretching sheet, incorporating the effects of magnetic field, porous medium, Brownian Motion, Thermophoresis and homogeneous chemical reaction. The governing nonlinear coupled ordinary differential equations for momentum, energy and nano particle concentration are derived using similarity transformations and solved via the shooting method integrated with a fourth order Runge-Kutta scheme. The impact of key physical parameters such as Casson parameter(β), Magnetic parameter(M), porous medium parameter(K_p),Brownian motion(N_b),       thermophoresis(N_t), Prandtl number(P_r), Lewis number(L_e), suction/injection(f_"w" ) and chemical reaction rate(K_c) on the velocity, temperature and concentration profiles is examined in detail. Results indicate that increasing the Casson parameter reduces fluid velocity, while higher thermophoresis enhances thermal boundary layer thickness. The numerical outcomes are validated through convergence studies and compared with existing literature, demonstrating good agreement. This comprehensive parametric investigation provides insight in to the transport behavior of non-Newtonian nanofluids relevant to industrial and biomedical applications