Ternary　boron　carbon　nitride　(BCN)　semiconductors　have　been　developed　as　emerging　metal-free　photocatalysts　for　visible-light　reduction　of　CO2,　but　the　achieved　efficiency　is　still　not　satisfying.　Herein,　we　report　that　the　CO2　photoreduction　performance　of　a　bulk　BCN　semiconductor　can　be　substantially　improved　by　surface　engineering　with　CdS　nanoparticles.　The　CdS/BCN　photocatalysts　are　characterized　completely　by　diverse　tests　(e.g.,　XRD,　FTIR,　XPS,　DRS,　SEM,　TEM,　N2　sorption,　PL,　and　transient　photocurrent　spectroscopy).　Performance　of　the　CdS/BCN　heterostructures　is　evaluated　by　reductive　CO2　conversion　reactions　with　visible　light　under　benign　reaction　conditions.　Compared　with　bare　BCN　material,　the　optimized　CdS/BCN　photocatalyst　exhibits　a　10-fold-enhanced　CO2　reduction　activity　and　high　stability,　delivering　a　considerable　CO　production　rate　of　12.5　μmol　h-1　(250　μmol　h-1　g-1)　with　triethanolamine　(TEOA)　as　the　reducing　agent.　The　reinforced　photocatalytic　CO2　reduction　activity　is　mainly　assigned　to　the　obviously　improved　visible-light　harvesting　and　the　greatly　accelerated　separation/transport　kinetics　of　light-triggered　electron-hole　pairs.　Furthermore,　a　possible　visible-light-induced　CO2　reduction　mechanism　is　proposed　on　the　basis　of　photocatalytic　and　photo(electro)chemical　results.　©　2018　American　Chemical　Society.