Porphyrins are a class of macromolecular heterocyclic compounds formed by the inter-carbon atoms of four pyrrole-like subunits through the submethyl bridge (〓CH▬). Porphyrin rings have 26 electrons in highly conjugated system and are easily modified peripheral structures, often serve as ideal building blocks to construct self-assembled nanostructures with excellent physical and chemical properties. Porphyrin nanostructures have excellent visible light absorption properties, which will significantly improve the efficiency of electron–hole separation, and are also commonly used in photocatalysis fields. Porphyrin photosensitizers have superior strong phototoxicity and little side effects, and are widely used in tumor photothermal/photodynamic treatment. This chapter summarizes the self-assembly methods of porphyrins, the applications progress of porphyrin self-assembled nanomaterials in photocatalysis and tumor therapy, and discusses the development trend in future of porphyrin nanomaterials.