Single-crystal organic nanowires were fabricated with a soft-template-assisted self-assembly method in liquid phase. These nanowires with rectangular cross section can serve as resonators for exciton-photon coupling, leading to a microcavity effect and a relatively low threshold of laser actions. Two-photon-pumped blue lasing was observed in these organic waveguiding nanostructures above a threshold of 60 nJ, excited with a 750 nrn near-infrared femtosecond pulse laser at 77 K.