A highly concentrated solution of polystyrene (PS) in N,N-dimethyl formamide (DMF) was electrospun and the surface morphology of the electrospun PS fibers was investigated. Unlike the porous morphology observed on the surface of the fibers electrospun from the PS solution in a volatile solvent, e.g. tetrahydrofuran, a regular protuberance morphology was found on the surface of the fibers electrospun from the PS solution in the non-volatile solvent, DMF. This unique surface morphology was formed due to the presence of residual DMF solvent inside the electrospun PS fiber. Due to the large diameter of the PS fibers (~5 to ~10 μm) formed from the highly viscous PS solution, the DMF could not evaporate completely from inside them during the electrospinning process. Therefore, the extrusive force of the residual solvent inside the fiber induced the formation of a unique surface morphology. We believe that this unique surface morphology increases the surface area of the electrospun fibers, thus making it possible to control their wetting or adsorption behavior.