Organic　thermally　activated　delayed　fluorescent　(TADF)　scintillators　hold　promising　potential　for　applications　in　medical　radiography　and　security　detection,　but　the　poor　X-ray　absorption　ability　and　inferior　radioluminescence　(RL)　hampered　their　progression.　Herein,　the　study　has　pioneered　the　development　of　high-performance　TADF　Ag(I)-based　scintillators　from　M2X2(dppb)2　(M　=　Ag,　Cu;　X　=　Cl,　Br,　I)　complexes　with　1,2-Bis(diphenylphosphino)benzene　(dppb)　ligand.　In　comparison　with　Cu(I)　complexes,　the　Ag(I)　series　generally　exhibited　superior　scintillation　performance.　Notably,　Ag2Cl2(dppb)2　(Ag1)　stands　out　with　exceptionally　high　RL　intensity　(≈125%　higher　than　that　of　CsI:Tl)　and　a　low　detection　limit　of　59.8 nGy s−1.　The　outstanding　scintillation　performance　of　Ag1　is　primarily　attributed　to　the　synergistic　effect　of　the　high　exciton　utilization　efficiency　origin　from　a　small　singlet-triplet　energy　gap,　enhanced　X-ray　absorption　capacity　by　heavy　atoms,　and　the　high　photoluminescence　quantum　yield　(76.47%　in　ambient　atmosphere).　By　fabricating　a　flexible　film　constructed　with　Ag1　submicron　crystalline　powders,　a　high　spatial　resolution　of　25.0 lp mm−1　for　X-ray　imaging　is　obtained.　It　offers　new　opportunities　for　utilizing　TADF　metal–organic　complexes　for　highly　efficient　X-ray　scintillation　and　imaging.　©　2024　Wiley-VCH　GmbH.