In recent years, much attention has been paid to biopolymers as an answer to the environmental issues and to the depletion of fossil resources. However, the application of biopolymers is often limited by their poorly mechanical and thermal properties. In order to be competitive to petroleum based polymers, they need to be modified. The attraction for cellulose nanowhiskers (CNW) as fillers in polymer matrices has largely increased due to the unique combination of their impressive mechanical properties with their high aspect ratio. Indeed, CNW offer many advantages such as high reactivity, renewability, biodegradability and natural abundance. Poly(lactic acid) (PLA) is one of the most representative bio-based and biodegradable polymers. However, some of its properties, like flexural properties and gas permeability are too low for widespread applications. The production of PLA/CNW bionanocomposites could be therefore, an efficient route to extend their utilization in many fields, with the possibility to adjust properties by filler content adjustment. In the field of textiles, the electrospinning process of various polymers filled with CNW is well documented including various polymeric matrices. Nevertheless, the need to develop new processing techniques, as an extension of conventional plastics industry, remains an important challenge. In this paper, melt spinning process was used to elaborate both neat PLA and PLA/CNW bionanocomposite fibers filled at 1 and 3 wt% in the presence of PLA-grafted-Maleic anhydride (PLA-g-MA) used as the compatibilizer at 7 wt%. The morphology and thermo-mechanical properties of the samples were investigated with respect to filler content ratio. PLA/CNW1 bionanocomposite fibers led to the best results compared to those filled at 3 wt%. Indeed at 1 wt%, SEM showed that CNW were homogeneously dispersed in the PLA matrix compared to 3 wt% loading and almost 18% increase in elongation at maximum force were obtained compared to neat PLA. In addition, a better thermal stability to PLA was observed.