The nano-fluids in view of the fabulous thermal conductivity enhancement have been recognized useful in several industrial and engineering applications. Present study provides an analytical investigation of the fluid flow, heat and mass transfer and entropy generation for the steady laminar non-Newtonian nano-fluid flow induced by a stretching sheet in the presence of velocity slip and convective surface boundary conditions using Optimal Homotopy Analysis Method (OHAM). In contrast to the conventional no-slip condition at the surface, Navier's slip condition is applied. The governing partial differential equations (PDEs) are transformed into highly nonlinear coupled ordinary differential equations (ODEs) consist of the momentum, energy and concentration equations via appropriate similarity transformations. Entropy generation equations, for the first time in this problem, are derived as a function of velocity, temperature and concentration gradients. The current OHAM solution demonstrates very good correlation with those of the previously published studies in the especial cases. The influences of different flow physical parameters on fluid velocity component, temperature distribution and concentration profile as well as the entropy generation number are discussed in details. Increasing the Brownian motion parameter and thermophoresis parameter, Biot number, Reynolds number, and Brinkman number or decreasing the Casson parameter and velocity slip parameter cause an increase in the entropy generation number. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.