Poly(3-alkylthiophene)s are known to self-assemble into well-ordered supramolecular assemblies. The organization influences the optical and electronic properties of these polymers. One way to induce supramolecular self-assembly is by lowering the solvent quality of solubilized poly(3-alkylthiophene) upon the addition of a non-solvent. Recently, the exact mechanism of the supramolecular self-assembly process has been explored for a chloroform/methanol (solvent/non-solvent) system. However, it is not clear how the solvent influences the supramolecular self-assembly mechanism. In this study, poly(3-alkylthiophene) is dissolved in two different solvents and the supramolecular self-assembly is fully explored by combining harmonic light scattering with electronic spectroscopy. Our results indicate that the actual supramolecular self-assembly is very different in both cases and that the choice of solvent has not only a significant influence on the assembly process but also on the structure of the final supramolecular assembly.