Dislocations (line defects) in ceramics and their effect on mechanical and functional properties have been neglected for a long time. Recently, multiple approaches have been adopted to engineer dislocations into ceramics without crack formation even at room temperature, among which is the wear test using a Brinell spherical indenter. These proofs-of-concept are yet still limited to single crystals (e.g. MgO and SrTiO₃) and with polycrystalline samples largely unexplored. For engineering applications, polycrystalline ceramics are highly relevant due to their much cheaper cost and easier fabrication. However, in polycrystalline ceramics the grain boundaries (GBs) pose a significant impact on the dislocation behaviour, especially pileup and cracking at GBs at room temperature due to the lack of sufficient independent slip systems. To achieve dislocation engineering in polycrystalline ceramics, it is critical to understand the underlying mechanisms of dislocation behaviour at and across GBs in ceramics. Here, we demonstrate that the wear tests across the ∑-5 GB in SrTiO₃ using millimeter-sized Brinell indenter can effectively produce numerous dislocations and suppress the crack formation, contrasting the indentation tests using the same indenter. Additionally, nanoscratch tests were performed in each grain to further investigate the activation of the slip systems and cracking, revealing a strong dependence of the length scale, crystallographic and scratching orientations. Some of these findings counteract the common picture of “brittle” ceramics and shed new light on the dislocation-GB interactions during wear tests of polycrystalline ceramics.