The assembly of π-conjugated molecule-based supramolecular micro/nanostructures is acknowledged as a versatile platform correlating supramolecular chemistry and soft matter science, wherein those with a spherical morphology are a topic of general concern. Most of the existing protocols, however, work only in some specific scenarios. It still remains a formidable challenge to initiate a general protocol for supramolecular micro/nanospheres of desired π-conjugated molecules. We herein report our new findings that numerous porphyrins and some other π-conjugated molecules, including phthalocyanine, anthracene, and naphthalenediimide derivatives, could be assembled to form micro/nanospheres via an oil-in-water-mediated surfactant-assisted assembly. As an example for the functionalization of the as-assembled structures, we show that a supramolecular light-harvesting antenna system with regard to photo-semiconductor-based heterogeneous photocatalysis could be achieved using porphyrin spheres. It is disclosed that the distinct chromophoric arrangements, which endow our porphyrin spheres with different photoinduced electron–hole separation capability, contribute greatly to their superior/inferior catalytic performances. Our new method might initiate a general method for advanced micro/nanospheres of desired π-conjugated molecules and desired functions.