We have demonstrated ultrasonic-assisted nanodimensional self-assembly of a conjugated polymer, P3HT, depending on its regioregularity, on solvent polarity, and on light irradiation. The resulting P3HT nanowires were investigated by means of AFM, UV−vis, and XRD and compared with films made by a conventional thermal annealing method. Obtained results indicate that ultrasonic agitation effectively generates P3HT nanowires, exemplifying a quick route to nanoscale morphology control which contributes to better organic photovoltaic cell performance.