The ferromagnetic topological insulator V:(Bi,Sb)₂Te₃ has been recently reported as a quantum anomalous Hall (QAH) system. Yet themicroscopic origins of the QAH effect and the ferromagnetism remain unclear. One key aspect is the contribution of the V atoms to the electronic structure. Here the valence band of V:(Bi,Sb)₂Te₃ thin films was probed in an element-specific way by resonant photoemission spectroscopy. The signature of the V 3d impurity band was extracted and exhibits a high density of states near the Fermi level,in agreement with spin-polaized first-principles calculations. Our results indicte the occurrence of a ferromagnetic superexchange interaction mediated by the observed impurity band, contributing to the ferromagnetism in this system.