<p>We report the abnormal spin Seebeck effect (SSE) observed in Tb₃Fe₅O₁₂(TbIG)/Pt heterostructures near the compensation temperature (<i>T</i>_comp) of TbIG. As the temperature approaches <i>T</i>_comp from room temperature, a rapid decline is shown in the spin Seebeck coefficient (SSC) from zero magnetic field to a high-field region, accompanied by its sign change. When the temperature decreases further below <i>T</i>_comp, magnon-polaron anomalies appear in the SSC near zero field. These temperature-sensitive abnormal SSE behaviors are supported by theoretical calculations, revealing the rotation of the net magnetic moment of Fe sublattices above <i>T</i>_comp and the magnon-polaron formation due to the hybridization of magnon and longitudinal acoustic phonon below <i>T</i>_comp. The observed abnormal SSE is related to the highly tunable noncollinear magnetic spin texture and its magnon dispersion. This work highlights the impact of diverse sublattice-dominated magnons on SSE, paving a new avenue for exploring the magnon spintronic devices in rare-earth iron garnets.</p>