The Classical Fourier's theory of heat flux is well-known in continuum physics and thermal sciences. However, the primary inconvenience of this law is that it contradicts the principle of causality. To investigate the thermal relaxation time characteristic, Cattaneo–Christov theory is assumed thermally. In this regard, the characteristics of magnetohydrodynamic (MHD) mixed convective flows of Casson nanofluids between two fixed impermeable parallel plates are revealed analytically and numerically. the resulting system of partial differential equations is changed via practical transformations into nonlinear ordinary differential equations. An advanced numerical algorithm is utilised in this study to get higher approximations for velocity and temperature fields, in addition to their corresponding wall gradients. For validating our numerical code, the current outcomes are compared with the other methods utilized in this work Akbari Ganji Method and Homotopy Perturbation Method. Moreover, it is revealed that the velocity field decreases for large values of casson and magnetic parametre. we can also see that Casson nanofluid is accelerated in case of lower yield strength. Larger values of thermal relaxation parameters create a lessening trend in the temperature distribution. The results of this study can help engineers improve, and researchers can conduct research faster and easier on this type of problem. also This work helps researchers to master the theoretical calculation of this type of problem.