Two chiral poly (3-alkylthiothiophene)s (P3ATTs) were prepared by polymerization of 2-bromo4-((S)-3,7-dimethyloctylthio)thiophene using a "modified McCullough method" (P1) and 2,5-dibromo-3-((S)-3,7-dimethyloctylthio)thiophene by the GRIM method (P2). PI was regioregular, while P2 was regio-irregular, as confirmed by H-1 NMR spectroscopy. The influence of the regioregularity on the chiroptical properties was investigated and they were compared with those of HT-poly(3-alkylthiophene)s and HT-poly(3-alkoxythiophene)s. UV-vis and circular dichroism spectroscopy revealed that both polymers self-organize into chiral supramolecular aggregates upon addition of a nonsolvent and in film. Remarkably, the regioregularity has (almost) no effect on the (chiral) supramolecular organization of poly (3-alkylthiothiophene)s.