Stimuli-responsive　materials,　showing　bistable　behaviors　between　two　distinct　states　under　external　stimuli,　can　be　potentially　applied　as　basic　components　of　modern　electrical　and　electronic　devices.　2D　hybrid　perovskites　hold　a　promise　to　switch　and　tune　dielectric　bistability　based　on　their　solid-state　phase　transitions.　Here,　strong　dielectric　enhancements　are　successfully　actualized　by　virtue　of　light　illumination　in　a　Dion-Jacobson　(DJ)　type　2D　hybrid　perovskite,　(HDA)(MA)2Pb3Br10　(1,　where　HDA　is　1,6-hexanediammonium　and　MA　is　methylammonium).　Upon　heating,　1　exhibits　an　ordered-disordered　phase　transition　approximate　to　324　K　(Tc),　accompanying　a　transition　from　its　low　to　high　dielectric　state.　Strikingly,　its　light-induced　dielectric　constant　changes　are　greatly　enhanced　with　a　magnitude　up　to　250%　near　the　Tc,　superior　to　most　traditional　inorganic　phase　transition　materials.　This　process　closely　relates　to　the　photoexcited　dielectric　effect　that　is　caused　by　the　interband　photo-excitation.　Benefitting　from　the　stability　of　DJ-type　perovskite　structure,　the　switching　cycles　of　dielectric　enhancement　display　operational　stability　with　superior　anti-fatigue　characteristics.　As　per　the　knowledge,　the　findings　of　this　strong　dielectric　enhancement　are　unprecedented　in　the　family　of　2D　DJ-type　hybrid　perovskites,　which　will　facilitate　broad　interest　in　exploiting　new　stimuli-responsive　materials　to　assemble　high-performance　smart　electronic　devices.　Dielectric　enhancement　is　actualized　by　virtue　of　light　illumination　in　a　2D　Dion-Jacobson-type　hybrid　perovskite,　for　which　the　light-induced　dielectric　constants　are　enhanced　with　a　magnitude　up　to　250%.　This　work　facilitates　the　exploration　of　new　stimuli-responsive　materials　to　assemble　high-performance　electronic　devices.　image