The activation energy (AE) of mixed convective, radiative magnetohydrodynamic Williamson nanofluid flow across an exponentially stretched sheet was investigated numerically. To convert the governing nonlinear partial differential equations into coupled ordinary differential equations, suitable similarity variables were introduced. The “Runge Kutta method” with the procedure of shooting was used to solve the resulting system of nonlinear ordinary differential equations with boundary conditions. The effects of various factors on profiles of nanoparticle volume fraction, temperature, and velocity were explored, and the results were presented graphically. The acquired results show that they are in great agreement with those found in the open literature. It is found that concentration profile is an increasing function of AE E whereas it decreases for chemical reaction rate constant σ* ${\sigma }^{* }$ and temperature difference δ $\delta $. It is also evident from the table that the local Sherwood number rises as the chemical reaction rate constant and temperature differences arise, and falls as the AE is enhanced.