We investigate the noise sensitivity of the top eigenvector of a Wigner matrix in the following sense. Let v be the top eigenvector of an N × N Wigner matrix. Suppose that k randomly chosen entries of the matrix are resampled, resulting in another realization of the Wigner matrix with top eigenvector v [k] . We prove that, with high probability, when k ≪ N 5/3−o(1) , then v and v [k] are almost collinear and when k ≫ N 5/3 , then v [k] is almost orthogonal to v.