Sunflower protein is among the most valuable proteins, constituting the main part of the sunflower meal. Forming complex between these proteins and dark phenolic compounds, make their use in food stuffs hard and they are usually discarded, so that, till now no commercial applications were suggested for them. In the present study, sunflower protein isolate (SPI) was extracted from the meal by the means of isoelectric sedimentation method. Protein nanofibers were fabricated by adding polyvinyl alcohol (PVA) (8%) to sunflower protein solution (16.6%).Then, the effects of two fundamental parameters, voltage (18 and 23 KV) and feed rate (0.5 and 0.75 mL/h) and also different ratios of SPI/PVA (100:0, 80:20, 60:40, 40:60, 20:80 and 0:100) on the fibers’ morphology and diameter were investigated. It was observed that uniform fibers with no beads or breakages were obtained by using SPI/PVA solution at ratio 60:40, voltage 18 KV and feed rate 0.75 mL/h which produce nanofibers with the average diameter of 398 nm. In order to apply fibers in food matrix (usually aqueous media), it’s necessary to make them hydrophobic. For this purpose, the effects of physical treatment by heating (150°C, 24h), chemical treatment by CaCl 2 (1%, 30 min soaking) and their combination were investigated. It was observed that only heating made nanofibers hydrophobic, since SEM images showed that after 24 h soaking in lactate buffer, fibers’ structure was maintained with no significant changes in diameter. Measuring the angle of water drop on nanofibers’ surface showed heating increased contact angle from 40° to 110°, which confirm hydrophobic nature of heated nanofibers. By comparison of FTIR and DSC/TGA analysis of fibers before and after heating, it was suggested that heat treatment caused ester bond formation between –COOH groups of protein and –OH groups of PVA which this reaction, beside egression of water molecules, make fibers hydrophobic. In order to vitamin D (VD) encapsulation, coaxial electrospinning method was applied using zein (20% solution) as a hydrophobic and spinnable polymer in the sheath and mixture of SPI (4%, 6% and 8%) and VD (5% and 10%) in the core of the fibers. Optimum fundamental parameters to produce core-shell fibers were voltage 14 KV and feed rate 0.5 mL/h. Consideration of SEM images revealed that coaxial fibers had ribbon-like, uniform and beadless morphology. Suitable fibers were produced using the mixture of 6% SPI/10% VD as the core, having the mean diameter of 723 nm. The core-shell structure was proved using TEM image. DSC/TGA analysis showed that coaxial fibers had more thermal resistance than emulsion ones and VD was well protected in the core of the fibers against destructive effects of the heat. FTIR spectra appeared that in both coaxial and emulsion fibers, VD was kept physically in the fibers’ matrix and no chemical interactions were happenedbetween it and other ingredients of the fibers. LC of the coaxial and emulsion fibers were measured 9.37% and 3.51% and EE were calculated 93.75% and 35.11%, respectively. These values indicated that VD was successfully encapsulated and protected by coaxial fibers. Consideration of VD release in lactate buffer it was evidenced that only 2.11% of total VD after 2h stirring in lactate buffer was released from coaxial fibers, whereas 91.0% of the VD was released from emulsion fibers. This event illustrated that VD was well protected in the coaxial fibers structure. The amount of released VD from coaxial and emulsion fibers in simulated gastric buffer were calculated 52.51% and 57.52%, respectively, and after final digestion in simulated intestinal buffer were reported 83.11% and 91.33%, respectively. Although, the ultimate amount of released VD from coaxial fibers was somewhat less than emulsion ones, but this amount was high enough and according to high stability of VD in the coaxial fibers’ structure due to full protection in the core of the fibers, it could be stated that coaxial electrospinning is an appropriate method for VD encapsulation in the SPI-zein core-shell fibers and release in the body. Studying VD release kinetics showed that for coaxial and emulsion fibers, VD release in gastric buffer followed by combination of diffusion and dissolution methods and in intestinal, gastro-intestinal and lactate buffers mainly, followed by diffusion. Key words: sunflower protein isolate, electrospinning, coaxial, hydrophobic, encapsulation, release, vitamin D.