Epoxidized natural rubber (ENR) fibers (ENRFs) were electrospun to obtain diameters ranging from a few hundred nanometers to a few micrometers by changing the ENR solution concentration. ENRFs were used to toughen soy protein isolate (SPI) based resin. A facile 1-step process was developed for wet electrospinning and blending the ENRFs directly into SPI resin. As the ENR concentration increased from 0.1% to 5%, the surface topography of ENRFs changed from irregular to somewhat bumpy. The average diameter of ENRFs also increased from 250 nm to 17 mu m. Increased ENRF (electrospun from 3% concentration) loading from 0 to 20% in SPI resin increased the fracture strain significantly from 1.7 to 18.8% and increased the toughness by a factor of 10. Interestingly, tensile strength and Young's modulus decreased only slightly compared to the increase in the toughness. Cross linking between the epoxy groups in ENR and amine and/or carboxylic groups in SPI as well as the high aspect ratio of the ENRFs contributed to increased toughness of SPI resin while retaining its tensile strength and Young's modulus. This research opens up possibilities of using fully green and toughened SPI resins in many applications including green composites.