Abstract Perovskite rare‐earth titanates RTiO 3 display a rich array of magnetic and electronic properties, with a Mott‐insulating ground state and ferro‐ or antiferromagnetic spin orders depending on the rare‐earth R. The nominal Ti valence is 3+ with a corresponding 3 d 1 configuration. Yet, at the surface of both bulk and thin films of RTiO 3 , the Ti valence has been found to strongly deviate towards the more stable 4+ state, adversely affecting magnetic properties. While this finding is rather ubiquitous, its exact origin is still poorly understood, which hampers the integration of RTiO 3 into complex heterostructures harnessing their rich physics. Here, scanning transmission electron microscope and electron energy loss spectroscopy experiments are used to analyze the top part of an epitaxial DyTiO 3 thin film displaying a well‐developed Ti 4+ ‐rich layer over several nanometres. It shows that this valence evolution is related to a combination of short‐range ordered interstitial oxygen planes and Ti‐Dy cationic imbalance. Both defects synergistically contribute to enough hole doping for a complete transition toward Ti 4+ over a few unit‐cells from the surface while a structure primarily of the perovskite‐type is maintained.