The　combination　of　photodynamic　therapy　and　other　cancer　treatment　modalities　is　a　promising　strategy　to　enhance　therapeutic　efficacy　and　reduce　side　effects.　In　this　study,　a　tamoxifen-zinc(II)　phthalocyanine　conjugate　linked　by　a　triethylene　glycol　chain　has　been　synthesized　and　characterized.　Having　tamoxifen　as　the　targeting　moiety,　the　conjugate　shows　high　specific　affinity　to　MCF-7　breast　cancer　cells　overexpressed　estrogen　receptors　(ERs)　and　tumor　tissues,　therefore　leading　to　a　cytotoxic　effect　in　the　dark　due　to　the　cytostatic　tamoxifen　moiety,　and　a　high　photocytotoxicity　due　to　the　photosensitizing　phthalocyanine　unit　against　the　MCF-7　cancer　cells.　The　high　photodynamic　activity　of　the　conjugate　can　be　attributed　to　its　high　cellular　uptake　and　efficiency　in　generating　intracellular　reactive　oxygen　species.　Upon　addition　of　exogenous　17β-estradiol　as　an　ER　inhibitor,　the　cellular　uptake　and　photocytotoxicity　of　the　conjugate　are　reduced　significantly.　As　shown　by　confocal　microscopy,　the　conjugate　is　preferentially　localized　in　the　lysosomes　of　the　MCF-7　cells.　©　2017　American　Chemical　Society.