The k‐th power of a graph G, denoted by Gk, is a graph with the same set of vertices as G such that two vertices are adjacent in Gk if and only if their distance in G is at most k. In this paper, we give the bounds on the spectral radius of Tk and Gk(k≥1). The Nordhaus–Gaddum‐type inequality for the spectral radius of the graph Gk is also presented. Moreover, we obtain an upper bound on the energy of the second power of graphs.