Conjugated self-assembled systems in water are of great interest because of their potential application in biocompatible supramolecular electronics, but so far their supramolecular chemistry remains almost unexplored. Here we present amphiphilic terthiophenes as a general self-assembling platform for the construction of conjugated aggregates, providing access to aggregates with different morphologies without changing the basic molecular design. We explored the design parameters of these amphiphilic terthiophenes in detail, leading to the selection and synthesis of in total 8 new amphiphilic oligothiophenes. Their aggregation behaviour was investigated by absorbance and fluorescence spectroscopy, dynamic light scattering, and cryo-transmission electron microscopy. Critical micelle concentrations as low as 0.01 mM were found and different sized aggregates ranging from several nanometres up to 200 nm. The aggregate morphology could also be tuned by changing the substitution pattern of hydrophilic and hydrophobic moieties, leading to different types of aggregates ranging from globular- and elongated micelles to bilayers. Remarkably, aggregation had only little effect on the electronic and spectroscopic properties of the oligothiophenes, which will be of interest for their application in supramolecular electronics.