The　trade-off　between　high　radioluminescence　(RL)　and　fast　decay　time　is　a　common　challenge　facing　almost　all　X-ray　scintillators.　Organic　fluorescence　scintillators,　with　ultrafast　response,　readily　available,　and　low　cost,　are　promising　for　imaging　and　detection.　Here,　organic　cocrystals　of　halogen-bonded　acceptors　and　donors　with　heavy　halogen　atoms　(Br　and　I)　are　designed　and　fabricated　to　achieve　high　RL　and　ultrafast　decay　time　simultaneously.　The　noncovalent　interactions　in　cocrystals　play　the　following　roles:　1)　The　strong　halogen　bonds　C≡N···X　(X　=　I,　Br)　promoted　X-ray　RL　by　providing　effective　pathways　for　electron　transfer,　whereas　the　relatively　weaker　C–X···π　do　not　contribute　to　this　enhancement.　2)　Halogen-bonded　donors　can　accelerate　fluorescence　decay,　resulting　in　ultrafast　decay　time　as　the　interaction　strength　increases.　3)　The　π–π　interactions　modified　their　molecular　packing　to　affect　fluorescence.　Through　the　modulation　of　these　noncovalent　interactions,　the　cocrystal　of　1,4-bis-p-cyanostyrylbenzene　(CSB)　and　1,4-diiodotetrafluorobenzene　(IFB)　exhibited　the　best　scintillation　performance　with　a　lifetime　of　0.58 ns　and　a　detection　limit　of　144.59 nGy s−1,　achieving　a　resolution　of　10 lp mm−1.　The　molecular　design　combined　with　the　cocrystallization　strategy　provides　new　insights　into　designing　scintillator　for　advanced　imaging　and　detection　applications.　©　2025　Wiley-VCH　GmbH.