This　study　applied　adaptive　negative　stiffness　devices　in　the　application　of　braced-damper　systems　to　propose　an　adaptive　negative　stiffness　amplifying　damper　(NSAD),　and　investigated　its　effectiveness　and　robustness　for　controlling　the　inelastic　seismic　responses　of　yielding　structures.　The　adaptive　stiffness　behavior　of　the　proposed　NSAD　perform　negative　stiffness　and　damping　magnification　effect　within　a　certain　displacement　threshold,　thus　controlling　both　structural　acceleration　and　drift　at　elastic　stage;　when　subjected　to　strong　earthquakes,　the　proposed　NSAD　would　adaptively　develop　positive　stiffness,　which　limits　the　inelastic　deformation　of　yielding　structures.　A　set　of　nonlinear　seismic　spectra　are　established　for　responses　including　acceleration,　ductility,　energy　dissipation,　and　residual　deformation.　Numerical　results　validated　that　the　proposed　adaptive　NSAD　is　effective　for　both　elastic　and　inelastic　structures.　In　addition,　influences　of　key　parameters　like　flexible　support,　negative　stiffness　ratio,　and　displacement　threshold　ratio　(ratio　of　displacement　threshold　to　yielding　displacement),　are　carefully　studied.　From　the　point　of　controlling　both　acceleration　and　ductility　demands　of　inelastic　structures,　the　displacement　threshold　ratio　is　recommended　to　have　a　value　close　to　a　unit;　typically,　a　reasonable　upper　limit　of　displacement　threshold　ratio　is　recommended　to　be　lower　than　1.5　to　avoid　amplifying　residual　deformation.　©　2022　John　Wiley　&　Sons　Ltd.