Supramolecular assemblies between cucurbit[n]uril macrocycles and a variety of conjugated polymers and porphyrins are reviewed in this chapter. The interactions between these macromolecules are based on the formation of inclusion complexes leading to the modification of some of its properties. Our focus herein is on the effect of cucurbit[n]urils on photophysical and photochemical properties of conjugated polymers and porphyrins. These supramolecular complexes hold great potential for applications in several areas, including light-emitting devices, optical sensors, photocatalysis and phototherapies. Conjugated polymers present great emissive properties, and they can be designed to possess antibacterial and/or phototoxic properties, both of which can be altered by complexation with cucurbit[n]urils. Modification of the photophysical properties occurs when the backbone is threaded through the cucurbit[n]urils, while complexation of the side chains can alter their toxicity. On the other hand, porphyrins are the standard molecules used in photodynamic therapy. These macrocycles not only provide a great solubilizing vehicle for porphyrins but modify their photophysical and photochemical properties such as singlet- and triplet-excited state lifetimes, emission quantum yields and singlet oxygen–generation capabilities. These novel supramolecular photosensitizers provide a way to reversibly control their photoactivity with great potential for their use in photodynamic therapy.