<p>In a recent scenario, the flow of non-Newtonian nanofluid for the impact of Brownian motion reveals a greater impact in various industries as well as engineering applications because of their effective properties. Based upon their physical properties, the present aim deals with the influence of bio-convection conducting the flow of non-Newtonian nanofluid through an elongating surface. The impact of activation energy along with the influence of the Williamson parameter enhances the study and gained significant attention due to their unique heat transfer characteristics and potential applications. Incorporating bio-convection, arising from microorganisms’ collective movement, adds complexity to the system. A stretching sheet, representing a practical engineering scenario, is considered as the boundary condition. The governing dimensional form of flow phenomena are converted to a non-dimensional form with the use of similarity variables. However, for the problem, a numerical approach is employed to solve the governing equations. The impact of key parameters such as the magnetic strength, activation energy, and bio-convection parameters on the fluid flow, heat transfer, and bio-convection patterns is systematically analyzed. Moreover, the important outcomes of the study are the non-Newtonian Williamson parameter that retards the fluid velocity but enhances the energy profile significantly, and the Brownian motion and thermophoresis due to the cross-diffusion also favor in enhancing the fluid temperature at all points within the domain.</p>