Abstract: The treatment of organic pollutants in aqueous environments is crucial to human health and sustainable development. The advanced oxidation process (AOP) exemplified by peroxymonosulfate (PMS) is a promising solution, and the emerging piezocatalytic technology may further promote high-efficiency degradation. This study employed a synergistic approach combining iron/cobalt/nickel-doped barium titanates and PMS to piezocatalytically degrade rhodamine B (RhB) solution. First, cubic and tetragonal BaTiO₃ calcined at different temperatures were systematically characterized. Scanning electron microscopy (SEM) was employed to demonstrate the micro-morphology of the materials. X-ray diffraction (XRD) analysis was used to verify the crystalline phase, and X-ray photoelectron spectroscopy (XPS) was utilized to characterize the valence of doping metals. Fourier-transform infrared spectroscopy was conducted to characterize the functional group on the surface of the materials. Piezoelectric force microscopy (PFM) was utilized to measure the piezoelectric performance of the materials. The results show that tetragonal BaTiO₃ exhibited better piezoelectric performance than cubic BaTiO₃, although its particle size was larger. Transition metals can activate PMS, while metal doping can enhance the piezoelectric performance of the material. To simultaneously improve both the AOP and piezocatalysis, we doped iron/cobalt/nickel into BaTiO₃. Different doping concentrations and different crystalline phases of iron/cobalt/nickel-doped BaTiO₃ were prepared, and XRD analysis revealed lattice distortion compared to pure BaTiO₃. RhB piezocatalytic degradation experiments show that metal-doped BaTiO₃ performed better than pure BaTiO₃. For iron/nickel-doped BaTiO₃, a 4% doping concentration produced better results than the 8% one, as the latter exceeded the optimum doping concentration. Materials calcined at 900 °C performed better than those calcined at 600 °C because the piezoelectric performance improved via the phase transition from cubic to tetragonal through high-temperature processing. Pure/iron/nickel-doped BaTiO₃ can achieve a degradation rate exceeding 97% for the RhB solution in 1.5 h. For cobalt-doped BaTiO₃, the degradation effect depended primarily on the activation of PMS by active cobalt sites. Compared with the 4% doping concentration, the 8% concentration produced better results, and calcination at 600 °C yielded better results than that at 900 °C. This is because the material surface provided more active cobalt sites: the former stemmed from a higher cobalt doping concentration, whereas the latter arose from a lower calcination temperature, which prevented particle fusion, thereby preserving a larger specific surface area. BaTiO₃ doped with 8% cobalt and calcined at 600 °C achieved 99.8% RhB degradation in 3 min. To elucidate the underlying mechanisms, radical scavenging experiments were conducted. Ethanol, 1,4-benzoquinone (BQ), and tert-butanol (TBA) were used to capture the sulfate radical ( \cdot \textSO_4^- ), superoxide radical ( \cdot \textO_2^- ), and hydroxyl radical ( \cdot \textOH ), respectively. The use of different free radical scavengers verified that pure/iron/nickel-doped BaTiO₃ depended on the piezocatalytic effect and that \cdot \textOH dominated the degradation process, whereas cobalt-doped BaTiO₃ depended on the activation of PMS by cobalt and \cdot \textSO_4^- dominated the degradation process. This study clearly presents two distinct degradation pathways within a similar material system and demonstrates that the activation of PMS by a specific transition metal such as cobalt can significantly dominate the process, whereas the piezocatalysis can play a supportive role. This study provides profound new insights and practical guidelines for the strategic integration of AOPs with piezocatalytic technology for efficient environmental remediation.