Uniform regio-regular poly(3-hexylthiophene) nanofibers and their blend nanofibers with poly (3-caprolactone) have been obtained by electrospinning and their electrical properties in single nanofiber field effect transistors have been compared. The key to the success was restricting the precipitation of P3HT at the nozzle tip, therefore preventing the nozzle from being clogged. The field effect mobility of pure P3HT fibers was 0.017 cm(2) V-1 s(-1) which is acceptable for device fabrication. Blend fibers with PCL also showed field effect behaviour with slightly degraded electrical properties by an order or two.