A mathematical analysis has been carried out for stagnation point heat and mass transfer of a viscoelastic fluid over a stretching sheet with surface slip velocity, concentration defendant diffusivity, thermal convective boundary conditions and heat source/sink. The governing partial differential equations are reduced to a system of non - linear ordinary differential equations using Lie group analysis. Numerical solutions of the resulting ordinary differential equations are obtained using shooting method. The influences of various parameters on velocity,temperature and mass profiles have been studied. Also, the effects of various parameters on the local skin-friction coefficient, the local Nusselt number and the local Sherwood number are given in graphics form and discussed.