AbstractDifferent SrTiO₃ thin films are investigated to unravel the nature of ultra‐low conductivities recently found in SrTiO₃ films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo‐intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively‐coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron‐based X‐ray standing wave and X‐ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe‐doped SrTiO₃ films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo‐intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (Fe_Sr and Ti_Sr) to accommodate nonstoichiometry. Sr vacancies act as mid‐gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably ) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self‐limitation of the Ti site change and leads to a very robust pseudo‐intrinsic situation, irrespective of Sr/Ti ratios and doping.