Alkaline-earth　dihalide　nanocrystals　(NCs)　such　as　SrFCl,　owing　to　their　high　chemical　stability　and　low　phonon　energy,　are　excellent　host　materials　for　lanthanide　(Ln3+)　doping　to　achieve　desirable　optical　properties　for　various　bioapplications.　Herein,　we　report　a　novel　strategy　for　the　synthesis　of　sub-10　nm　Ln3+-doped　SrFCl　NCs　with　efficient　upconverting　and　downshifting　luminescence　through　a　facile　one-step　hot-injection　method.　Utilizing　the　temperature-dependent　upconverting　luminescence　(UCL)　from　the　thermally　coupled　2H11/2　and　4S3/2　levels　of　Er3+,　we　showed　the　potential　of　SrFCl:Yb,Er　NCs　as　sensitive　UCL　nanoprobes　for　non-contact　thermal　sensing　with　a　maximum　detection　sensitivity　of　0.0066　K–1,　which　is　among　the　highest　values　for　thermal　sensing　based　on　Er3+-activated　UCL　nanoprobes.　Furthermore,　by　employing　the　intense　downshifting　luminescence　from　Tb3+　and　Eu3+,　we　demonstrated　the　successful　use　of　biotinylated　SrFCl:Ce,Tb　and　SrFCl:Eu3+　nanoprobes　for　biotin　receptor-targeted　cancer　cell　imaging,　thus　revealing　the　great　promise　of　SrFCl:Ln3+　nanoprobes　for　versatile　bioapplications.　©　2019　Chinese　Society　of　Rare　Earths