In this paper, the buoyancy effect on flow and heat transfer characteristics of nanofluid in presence of carbon nanotubes due to a vertical plate is investigated. The obtained nonlinear PDE’s are converted to the non-linear ordinary differential equations by applying the similarity transformations corresponding to the boundary conditions. These boundary value problems are solved numerically using fourth order Runge-kutta method together with the efficient shooting iteration scheme. The nature of the flow and heat transfer are plotted and discussed in detail. It is noticed that buoyancy effect is very useful in cooling the system and present results compared with previously published result, our results are in very good agreement for some limiting cases.