In this paper, the thermal radiation and magnetic field effects on unsteady heat, mass, and fluid flow over a horizontal stretching surface have been obtained and studied numerically. The governing continuity, momentum, energy, and concentration equations were converted into a system of nonlinear ordinary differential equations by means of similarity transformation. The resulting system of coupled nonlinear ordinary differential equations was solved numerically. Numerical results were presented for velocity, temperature, and concentration profiles for different parameters of the problem as unsteadiness parameter, radiation parameter, magnetic field parameter, temperature buoyancy parameter, Prandtl parameter, heat source parameter, Schmidt parameter, chemical reaction parameter, Lewis number, and others. Also, the effects of the pertinent parameters on the skin friction, the rate of heat, and mass transfer were obtained and discussed numerically, and illustrated graphically