We study the robustness under perturbations of mixing times, by studying mixing times of random walks in percolation clusters inside boxes in Z d . We show that for d ≥ 2 and p > p c (Z d ), the mixing time of simple random walk on the largest cluster inside {-n, . . . , n}d is Θ(n 2 ) – thus the mixing time is robust up to a constant factor.