The new investigation delivers the consequence of viscous dissipation and Soret effects on hydromagnetic mixed convection flow across a porous medium bounded by infinite vertical plates. The flow considered is fully developed time-dependent. Viscous dissipation causes variations in fluid temperature and fluid properties. Energy loss due to viscous dissipation is treated by the heat equation. The PDEs that are coupled and nonlinear are simplified to ODEs. The transformed equation incorporates interrelated boundary conditions that are analytically resolved by methods of perturbation. Estimated solutions for flow speed, temperature, concentration field are discussed. The impressive findings are: growing interest in magnetic parameter reduces the dimensionless velocity. Also, the formation of a thin boundary layer is observed for a higher value of the magnetic parameter. Eckert number, Soret number cause an increase in the velocity and concentration profiles of the flow. The impacts of these relevant factors on Shear stress, Nusselt number and Sherwood number are also evaluated and described quantitatively in tabular representations. Comparing the current analysis with those of previously published work shows excellent agreement.