This study deals with the effect of variable viscosity and Prandtl number on the steady, laminar free convection flow (of iso-propanol) past a vertical porous flat plate. The coupled nonlinear partial differential equations governing the self-similar flow have been solved numerically using an implicit finite difference scheme in combination with the quasilinearization technique. Numerical results indicate that variable viscosity (and Prandtl number) has a major role on skin friction and heat transfer parameters as well as velocity and temperature fields. Further, it is observed that the effect of variable fluid properties plays a significant role in the control of laminar boundary layer. The present analysis reveals the fact that when the working fluid is sensitive to the temperature, the effect of variable viscosity and Prandtl number has to be taken into the consideration in order to predict the skin friction and heat transfer rate, accurately.