Photodynamic therapy (PDT) of cancer is limited by tumor hypoxia. Platinum nanoparticles (nano-Pt) as a catalase-like nanoenzyme can enhance PDT through catalytic oxygen supply. However, the cytotoxic activity of nano-Pt is not comprehensively considered in the existing methods to exert their multifunctional antitumor effects. Here, nano-Pt are loaded into liposomes via reverse phase evaporation. The clinical photosensitizer verteporfin (VP) is loaded in the lipid bilayer to confer PDT activity. Murine macrophage cell membranes are hybridized into the liposomal membrane to confer biomimetic and targeting features. The resulting liposomal system, termed "nano-Pt/VP@MLipo," is investigated for chemophototherapy in vitro and in vivo in mouse tumor models. At the tumor site, oxygen produced by nano-Pt catalyzation improves the VP-mediated PDT, which in turn triggers the release of nano-Pt via membrane permeabilization. The ultrasmall 3-5 nm nano-Pt enables better penetration in tumors, which is also facilitated by the generated oxygen gas, for enhanced chemotherapy. Chemophototherapy with a single injection of nano-Pt/VP@MLipo and light irradiation inhibits the growth of aggressive 4T1 tumors and their lung metastasis, and prolongs animal survival without overt toxicity.