Exploration　of　nonlinear　optical　(NLO)　crystalline　materials　is　a　hot　and　continuing　research　topic　in　modern　optoelectronics　and　laser　technology.　Within　this　portfolio,　the　emerging　organic-inorganic　hybrid　metal　halides　provide　infinite　opportunities　due　to　their　fascinating　advantages　of　inorganic　metal　frameworks　and　organic　molecules.　Herein,　by　cooperatively　combining　the　inorganic　second-order　Jahn-Teller　distorted　octahedron　[SbCl6]　and　the　organic　π-conjugated　aromatic　amine　(N,N,4-trimethylaniline,　C9H13N),　a　non-centrosymmetric　(NCS)　organic-inorganic　hybrid　antimony　halide,　(C9H14N)SbCl4,　has　been　developed.　Meanwhile,　the　bulky　colorless　single　crystals　of　(C9H14N)SbCl4with　dimensions　of　10　×　3　×　0.5　mm3are　grown　by　the　temperature-lowering　crystallization　process.　Further　optical　property　investigations　reveal　that　the　crystals　possess　a　remarkable　second　harmonic　generation　(SHG)　response　(2.1　×　KDP,　KH2PO4)　and　a　moderate　birefringence　(0.095@546　nm)　to　achieve　phase-matching　behavior,　and　they　demonstrate　promising　prospects　for　application　in　the　NLO　field.　Furthermore,　the　crystal　structure　analysis　and　theoretical　calculations　demonstrate　that　the　large　SHG　response　primarily　originates　from　the　cooperative　coupling　between　the　highly　asymmetric　distorted　[SbCl6]　octahedron　(3.649　×　10-3)　and　the　π-conjugated　aromatic　amine.　This　work　points　out　an　efficient　route　for　the　future　exploration　of　new　quadratic　NLO　materials　with　excellent　optical　performance　in　hybrid　metal　halides.　©　2022　American　Chemical　Society.　All　rights　reserved.