The study of boundary layer flow of Casson fluid with heat transfer over a nonlinear stretching sheet is studied. The Non-Newtonian Casson fluid obeys the equation of state due to the Casson model.The system of nonlinear partial differential equations which control these flow behaviors is solved by using perturbation technique. The velocity and the heat distributions are obtain for corresponding parameters with the help of computer programming Compaq Visual Fortran (6.6a) and the figure have been drawn by Tec plot (9.0).