Immune　checkpoint　inhibitors　represented　by　PD-1/PD-L1　monoclonal　antibodies　have　shown　great　success　in　tumor　immunotherapy.　However,　the　response　rate　of　immune　checkpoint　blockade　(ICB)　therapy　alone　is　far　from　satisfactory　due　to　insufficient　and　exhausted　tumor-infiltrating　T　cells.　Meanwhile,　antibody-based　drugs　have　some　drawbacks　such　as　high　cost　and　complicated　preparation,　which　require　further　development　of　nonantibody　immune　checkpoint　inhibitors　and　more　rational　strategies　for　improving　the　effectiveness　of　tumor　treatment.　Here,　a　highly　efficient　bifunctional　peptide　(Bi-pep)　was　constructed　for　tumor　treatment　by　simultaneously　activating　T　cells　and　blocking　the　PD-L1　immune　checkpoint.　This　peptide　not　only　can　block　the　PD-1/PD-L1　immunosuppressive　pathway　but　also　directly　and　efficiently　promote　the　activation　and　proliferation　of　T　cells,　thereby　showing　a　significant　effect　on　promoting　T　cell　killing　of　tumor　cells.　The　Bi-pep-induced　antitumor　effect　was　verified　on　both　subcutaneous　and　orthotopic　tumor　models,　which　can　significantly　inhibit　tumor　growth　and　thus　prolong　the　survival　of　tumor-bearing　mice,　holding　great　potential　for　biomedical　applications.　©　2025　American　Chemical　Society.