A fully elliptic numerical study was performed to investigate the buoyancy-affected, three-dimensional turbulent flow and heat transfer in the entrance region of a curved pipe. The renormalization group (RNG) k-epsilon model was used to simulate the turbulent flow and heat transfer in the pipe. A dimensionless ratio parameter, root Gr/D(n)root 1 + Pr, was employed to characterize the relative magnitude of buoyancy and centrifugal effect on the secondary flow in the curved pipe. The computed results for forced convective flow and heat transfer show agreement with previous experimental data. It was found that the distribution of axial velocity and temperature rotated clockwise to a different extent depending on the ratio of root Gr/D(n)root 1 + Pr. At higher Grashof numbers, the developing secondary how field showed the existence of three vortices. The peripherally averaged Nusselt number and friction factor exhibit oscillatory behavior along the streamwise direction. The augmentation of the average Nusselt number and friction factor resulting from buoyancy was prominent at the entrance region of the pipe, but gradually became weaker further downstream.