The present study deals with the effect of slip on the heat transfer and entropy generation characteristics of viscoelastic fluids in a channel. The slip has been modeled using three different slip laws namely, Navier’s nonlinear slip law, Hatzikiriakos slip law and asymptotic slip law. The viscoelastic nature of the fluid is captured using the linear version of simplified Phan-Thien-Tanner (s-PTT) model. The flow is assumed to be hydrodynamically and thermally fully developed with uniform heat flux boundary condition at the wall. Viscous dissipation is included while axial conduction is ignored. The governing equations have been solved analytically and the reasons behind the observed trends have been explained in detail. Specifically, Nusselt number shows a complex dependence on the viscoelastic group, slip coefficients and the pressure gradient. Finally, a comparison between Hatzikiriakos slip law and the asymptotic slip law shows that the slip velocity and consequently the Nusselt number is higher for Hatzkiriakos version of slip law