In this article, we establish a mathematical relation for unsteady 3D flow of a magneto-Carreau liquid over a bidirectional stretched surface. The impact of convective heat transfer for magneto-Carreau liquid is investigated in the presence of non-linear thermal radiation and heat absorption/generation. Additionally, in this analysis, the proposed model of heterogeneous–homogeneous processes with equivalent diffusivities for reactant and autocatalysis is considered. The modeled boundary layer equations are reduced to a system of nonlinear ordinary differential equations using the appropriate transformation. The resulting equations are then solved by utilizing two different techniques, namely the bvp4c function in Matlab and homotopy analysis method (HAM). The numerical data for the velocity, temperature and concentration fields are graphically sketched and characteristics of the relevant parameters are deliberated in detail. Moreover, the velocity gradients and the rate of heat transfer at the stretched surface for different values of the pertaining parameters are given in tabulated form. It is observed that the temperature profile enhance for higher values of magnetic parameter M and heat generation parameter $$(\delta >0)$$ , whereas it decline for augmented values of heat absorption $$(\delta <0)$$ parameter. In addition, the concentration profile decline for increasing values of homogeneous reaction parameter $$k_{1}$$ and unsteadiness parameter S. To see the validity of the numerical computations, we compared these results of the numerical techniques bvp4c with an efficient analytical method, namely the homotopy analysis method (HAM) and perceived an outstanding correlation between these techniques.