Photodynamic　therapy　(PDT)　is　a　minimally　invasive　treatment　that　utilizes　a　photosensitizer,　specific　light　wavelengths,　and　oxygen　to　generate　reactive　oxygen　species　(ROS),　causing　oxidative　damage　and　tumor　cell　death.　However,　the　effectiveness　of　PDT　can　be　reduced　by　the　intrinsic　antioxidant　and　DNA　repair　mechanisms　of　tumor　cells.　Artemis　(SNM1C/DCLRE1C)　is　an　endonuclease　essential　for　repairing　DNA　double-strand　breaks　(DSBs)　via　non-homologous　end-joining　(NHEJ).　Herein,　we　conducted　a　high-throughput　small-molecule　screening　and　identified　Punicalagin　(PUG),　a　natural　polyphenol　from　pomegranate,　as　a　novel　Artemis　inhibitor　with　an　IC50　value　of　296.1　nM.　We　also　investigated　the　effects　of　PUG　combined　with　PDT　in　tumor　treatment,　using　the　pentalysine　(3-carbonylphthalocyanine　zinc　(ZnPc5K)　as　the　photosensitizer.　In　HeLa　cells,　ZnPc5Kbased　PDT　induced　significant　DSBs,　which　could　be　repaired　by　the　intrinsic　DNA　repair　mechanisms　within　12　h.　Co-treatment　with　PUG　compromised　DNA　repair,　promoted　cell　apoptosis,　inhibited　cell　invasion,　and　suppressed　the　growth　of　various　tumor　cells.　Furthermore,　in　a　mouse　xenograft　model,　the　combination　of　PUG　and　ZnPc5K-PDT　effectively　inhibited　tumor　growth　with　minimal　side　effects.　These　findings　suggest　that　PUG,　as　an　Artemis　inhibitor,　can　enhance　the　therapeutic　efficacy　of　PDT　in　tumor　suppression　by　impairing　DNA　repair　through　the　NHEJ　pathway.