Black　phosphorus　(BP)　has　emerged　as　a　rapidly　rising　star　in　the　field　of　biomedical　science.　In　this　work,　BP　nanosheets　(BPNSs)　are　synthesized　and　their　potential　as　a　nano-antibacterial　agent　is　investigated.　The　concentration　and　time-dependent　antibacterial　activities　are　evaluated　by　cell　viability　assays　together　with　scanning　electron　microscopy,　confocal　laser　scanning　microscope,　and　the　measurement　of　efflux　of　RNA　release　assay.　The　experimental　results　show　that　BPNSs　have　a　strong　killing　effect　on　both　representatives　of　gram-negative　bacteria　(Escherichia　coli)　and　gram-positive　bacteria　(Staphylococcus　aureus),　and　exhibit　concentration　and　time-dependent　antibacterial　activity.　The　sharp　edges　of　BPNSs　in　the　interaction　with　bacteria　can　cause　physical　damage　to　the　bacterial　membrane　and　RNA　leakage,　resulting　in　bacterial　death.　The　results　demonstrate　that　the　BPNSs　show　great　promise　as　new　nano-antibacterial　materials.　©　2020　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim