Under suitable restrictions on the higher order mean curvatures, we establish uniqueness results for entire graphs in a warped product space satisfying a standard convergence condition. Consequences are given for such graphs to be slices by using comparison inequalities of their higher order mean curvatures. Applications to the study of the rigidity of minimal and radial graphs in the Euclidean space are also given. (C) 2015 Elsevier Inc. All rights reserved.