This study is focused on the joint effects of thermal radiation and magnetic field on an unsteady flow of natural convective, electrically conducting fluid past an irregular vertical channel in the presence of viscous dissipation. The magnetic field is applied normal to the channel. The coupled ordinary differential equations (ODE) are obtained using perturbation technique on the dimensionless governing equations involving energy and momentum equation. Semi-analytical solutions are obtained for the resultant coupled ODE with the application of Adomian Decomposition Method (ADM) with the aid of Mathematica 11.0 software. The pertinent flow parameters in velocity, temperature, Skin-friction and Nusselt number are discussed and exhibited using tables and graphs. It is revealed that at all regions, thermal radiation a nd viscous dissipation have a tendency to accelerate the Skin-friction and heat transfer coefficient of the fluid.