We report monoaxial electrospinning and self-assembly characterization of poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) nanofibers. Nanofibers were directly compared to films (as made and annealed) to understand the effects of extensional forces and high evaporation rate inherent to electrospinning on nanoscale structure. X-ray scattering shows electrospinning can achieve improved crystallinity and reduced length scale of P3HT and PCBM phases. Due to extensional flow, co-continuous phases form along the fiber axis, as evident in transmission electron microscopy. To our knowledge, this is the first study to investigate monoaxially-spun, pure P3HT/PCBM nanofibers, a facile processing method with the potential to transform the field of wearable photovoltaics.