The unsteady flow along with the heat transfer of a thin Newtonian liquid film is examined concerning a horizontal stretching surface. The impact of flow unsteadiness, Lorentz forces, wall slip, viscous dissipation, heat/sink sources and thermal radiation are examined by utilizing a similarity transformation. In particular, non-linear ordinary differential equations are derived via reducing of the boundary layer equations and solved numerically via shooting method. It is deduced that as the magnetic field is intensified, the fluid decelerates and consequently the free surface temperature increases due to the gradual prevail of conduction over convection, while the film thickness tends to shrink. Besides, the film thickness seems to decrease for larger values of unsteadiness parameter and larger values of slip. Finally, convection heat transfer is found to be enhanced as the slip and the source parameters decrease and diffusion, viscous dissipation as well as thermal radiation increase.