This computation reports the mixed convection flow of Williamson fluid past a radially stretching surface with nanoparticles under the effect of first-order slip and convective boundary conditions. The coupled nonlinear ordinary differential equations (ODEs) are obtained from the partial differential equations, which are derived from the conservation of momentum, energy, and species. Then, utilizing suitable resemblance transformation, these ODEs were changed into dimensionless form and then solved numerically by means of a powerful numerical technique called the Galerkin finite element method. The effect of different parameters on velocity, temperature, and concentration profiles is inspected and thrashed out in depth by graphs and tables. The upshots exhibit that the velocity profile augments as the values of concentration buoyancy and mixed convection parameters are engorged. Also, the results demonstrated that both temperature and concentration profiles are improved with an enhancement in values of thermophoresis parameters. The outcomes also indicate that for finer values of magnetic field parameter and thermophoresis parameter, the numerical value of local Nusselt and Sherwood numbers is reduced. K E Y W O R D S finite element method, mixed convection flow, nanofluid, radially stretching surface, Williamson fluid