Cellulose nanocrystals (CNCs), a kind of biocompatible and biodegradable nanofiller, were prepared by sulfuric-acid hydrolysis of commercial alpha-cellulose. CNC/ polycaprolactone (PCL) nanocomposite fiber mats were produced via electrospinning and characterized by scanning electron microscopy, differential scanning calorimetry (DSC) analysis, thermogravimetric analysis (TGA), uniaxial tensile tests, and static water-contact-angle analysis. The results showed the mechanical properties and thermal stability of the nanocomposite fiber mats were improved and the surface hydrophilicity was increased in comparison with neat PCL fiber mats.