This paper describes the enhancement in stability and electrochromic properties of regioregular poly(3-hexylthiophene) (rrP3HT) polymer films in ambient conditions via ultrasonication of the polymer solution before deposition. The ultrasonicated polymer solution was spin coated onto an ITO substrate, and the electrochromic properties of the resulting rrP3HT films were characterized by UV-Vis spectroscopy, cyclic voltammetry and spectroelectrochemistry. The morphology and crystallinity of the polymer films were measured by atomic force microscopy and X-ray diffraction. Ultrasonication of the polymer solution controlled and increased the intra-chain interaction of the resulting polymer film on an ITO substrate. This method resulted in the polymer film changing colors at a voltage 0.2 V less than an untreated film with concurrent high stability and a fast response switching time of 1-2 s. This method was demonstrated to be a convenient way to lower the applied voltage and to increase the stability of the electrochromic rrP3HT film.