For α ∈ [0, 1], let A α (G) = αD(G)+(1−α)A(G) be A α -matrix, where A(G) is the adjacent matrix and D(G) is the diagonal matrix of the degrees of a graph G. Clearly, A 0 (G) is the adjacent matrix and 2A 1 2 is the signless Laplacian matrix. A connected graph is a cactus graph if any two cycles of G have at most one common vertex. We first propose the result for subdivision graphs, and determine the cacti maximizing A α -spectral radius subject to fixed pendant vertices. In addition, the corresponding extremal graphs are provided. As consequences, we determine the graph with the A α -spectral radius among all the cacti with n vertices; we also characterize the n-vertex cacti with a perfect matching having the largest A α -spectral radius.