In this study, an analysis has been performed for heat and mass transfer with radiation effect in transient laminar boundary layer flow of a viscous fluid past an impulsively moving infinite vertical flat plate in a homogenous porous medium in the presence of thermal diffusion and heat source/sink. Exact solution of momentum, energy and diffusion equations, under Boussinesq approximation, is obtained in closed form by use of Laplace transform technique. The variations in fluid velocity, temperature and concentration distribution are shown graphically, whereas numerical values of skin-friction, Nusselt number and Sherwood number are presented in tabular form and discussed