In　this　work,　the　structural　and　magnetic　properties　of　Cr　doping　at　possible　sites　in　the　InS　monolayer　were　systematically　investigated　by　density　functional　theory.　The　pristine　InS　monolayer　is　a　diamagnetic　semiconductor　material　of　an　indirect　band　gap.　Based　on　our　results,　doping　of　the　Cr　atom　at　possible　lattice　sites　in　the　InS　monolayer　tuned　the　band　gap　and　induced　ferromagnetism　in　a　diamagnetic　InS　monolayer.　Furthermore,　the　dopant　atom　induces　impurity　states　within　the　band　gap　of　the　pristine　InS　monolayer.　Thermodynamically,　Cr-In　is　the　most　stable　site　among　all　possible　doping　sites　under　growth　conditions.　Therefore,　we　chose　the　In　site　for　further　investigations.　The　InS　monolayer　doped　with　Cr　at　the　S　site　shows　a　half-metallic　nature,　which　is　the　basic　need　for　the　next　generation　of　spintronic　devices.　Finally,　we　studied　the　ferromagnetic　(FM)　and　anti-ferromagnetic　(AFM)　interactions　of　dopant　atoms　by　varying　the　interaction　length　between　the　two　dopant　sites.　To　estimate　the　Curie　temperature　T-c,　the　calculated　exchange　coupling　parameter　J=1.056　meV　for　two　Cr　atoms　doped　at　far　positions.　We　found　that　two　Cr　atoms　lying　at　the　near　separation　distance　prefer　the　AFM　state,　while　two　Cr　atoms　lying　at　the　far　separation　distance　prefer　the　FM　state.　T-c　estimated　for　the　latter　arrangement　is　8.17　K　(45.27　K)　at　equilibrium　(-3%　biaxial　strain).　We　conclude　that　the　substitutional　doping　of　Cr　atom(s)　in　the　2D　InS　monolayer　improved　their　electronic　and　magnetic　properties,　indicating　that　InS:Cr　is　a　potential　candidate　for　spintronic　devices.　[GRAPHICS]　.