A study has been carried out to analyse an unsteady free convective chemically reacting, MHD Visco-elastic fluid (Walter’s liquid-B model) flow past an infinite vertical plate in the presence of thermal radiation with uniform temperature and species diffusion. The dimensionless governing partial differential equations are solved by using Laplace transform technique. The effects of different physical parameters like visco-elastic parameter, chemical reaction parameter, Magnetic field parameter, thermal Grashof number, mass Grashof number and time are discussed by plotting the velocity profiles for both cooling (Gr > 0, Gm>o) and heating of the plate (Gr > 0, Gm>o) while the temperature, concentration, Sherwood number and Nusselt number also analysed through graphs. It is observed that increasing viscoelastic and chemical reaction parameter the velocity is increasing for cooling of the plate but the reverse effect to be found in heating of the plate. An increase in the Prandtl number and radiation parameter is found to decrease the velocity and temperature but increasing in Nusselt number. © 2017, Global Digital Central. All Rights Reserved.