The off-centering effect in thermoelectric materials has been recently discovered and is characterized by the displacement of lattice atoms from their ideal coordination centers, leading to local distortion and symmetry breaking. This effect is a primary cause of ultralow thermal conductivity and can be leveraged to enhance thermoelectric performance. The paper discusses various off-centering compounds, their electronic origins, and local coordination structures. It highlights how off-centering introduces low-frequency optical modes, enhancing acoustic-optical (A-O) phonon scattering, which reduces thermal conductivity. The mechanism is illustrated through examples such as PbTe, AgGaTe₂, and cubic metal halide perovskites, where off-centering is driven by lone pair electrons, weak orbital hybridization, oversized coordination environments, and weak chemical bonding. The off-centering effect provides a new strategy for designing high-performance thermoelectrics by effectively reducing thermal conductivity.The off-centering effect in thermoelectric materials has been recently discovered and is characterized by the displacement of lattice atoms from their ideal coordination centers, leading to local distortion and symmetry breaking. This effect is a primary cause of ultralow thermal conductivity and can be leveraged to enhance thermoelectric performance. The paper discusses various off-centering compounds, their electronic origins, and local coordination structures. It highlights how off-centering introduces low-frequency optical modes, enhancing acoustic-optical (A-O) phonon scattering, which reduces thermal conductivity. The mechanism is illustrated through examples such as PbTe, AgGaTe₂, and cubic metal halide perovskites, where off-centering is driven by lone pair electrons, weak orbital hybridization, oversized coordination environments, and weak chemical bonding. The off-centering effect provides a new strategy for designing high-performance thermoelectrics by effectively reducing thermal conductivity.