Increasing　Investigations　show　that　photosensitizers　(PSs)　which　target　mitochondria　are　useful　for　enhancing　photodynamic　therapy　(PDT)　efficacy.　Herein,　we　carefully　designed　and　synthesized　four　triphenylphosphonium　(TPP)-modified　boron　dipyrromethene　(BDP)-based　PSs　through　Cu(I)-assisted　“3+2”　cycloaddition　reaction.　All　of　them　exhibit　intense　red　light　absorption　with　maxima　between　659　and　663　nm,　considerable　fluorescence　emission　with　quantum　yields　of　0.16–0.23,　high　singlet　oxygen　generation　efficiency　ranging　from　0.22　to　0.34,　excellent　mitochondria-targeting　ability,　and　good　biocompatibility.　Upon　illumination,　they　induce　significant　cancer　cell　death　through　a　mitochondria-related　apoptosis　pathway.　The　IC50　values　of　these　BDP　dyes　against　MCF-7　cells　were　determined　to　be　as　low　as　0.046–0.113　μM　under　rather　low　dosage　of　light　irradiation　(1.5　J　⋅　cm−2).　©　2022　Wiley-VCH　GmbH.