We investigated the electronic and magnetic ground states of the cage compound FeGa3 under the presence of Fe antisite disorder (namely as Fe0.258Ga0.742) by x-ray diffraction (XRD), Mössbauer spectroscopy (MS), magnetization and electrical resistivity. Our results show that approximately 4.5 (5)% Fe antisite occupying one of the two non-equivalent Ga sites changes significantly the electronic and magnetic ground states of the pristine compound. We uncover that Fe0.258Ga0.742 undergoes two magnetic transitions, T1 ≈ 60 K and T2 ≈ 15 K, the latter associated with the suppression of semiconducting behavior. We focus our discussion on the role that in-gap impurity states and spin disorder play across semiconducting-metal and paramagnetic-magnetic transitions.