A　small　electrocaloric　effect　(ECE)　is　usually　observed　in　aliovalent　doped　ferroelectric　ceramics　since　decreased　polarization　is　usually　present.　In　this　work,　the　high　ECE　is　achieved　in　a　barium　titanate　[BaTiO3　(BT)]-based　ceramic　by　introducing　defect　polarization　to　enhance　the　ferroelectric　polarization　and　polarization　change.　The　defect　dipoles　consisting　of　donor　ion　and　barium　vacancy,　or　barium　and　oxygen　vacancies　were　formed　in　samarium-doped　(Ba1−1.5xSmx)TiO3　ceramics.　The　phase　and　defect　structures,　and　dielectric　and　ferroelectric　properties　are　analyzed　to　confirm　the　evolution　of　charge　compensation　states　and　defect　structures,　and　the　influences　of　defects　on　polarization　rotation　and　ECE.　An　enhanced　ferroelectric　polarization　and　high　internal　bias　field　are　present　in　the　ceramic　with　a　suitable　defect　dipole　effect,　leading　to　a　high　polarization　change　before/after　applying　an　electric　field,　causing　an　enhanced　ECE.　Finally,　a　high　electrocaloric　temperature　change　of　∼1.11　K　and　a　large　electrocaloric　strength　of　∼0.037　K·cm　kV−1　were　achieved　under　a　low　electric　field　of　30　kV/cm,　indicating　that　forming　suitable　defect　dipoles　can　optimize　the　ECE.　This　work　provides　a　significant　paradigm　for　tuning　ECE　in　ferroelectric　materials　via　defect　regulation.　©　2024　Elsevier　B.V.