Aramid and other high strength fibers and fabrics have been studied extensively due to their application in a wide range of products such as bullet-proof vests, confinement chambers for jet engines, cut-resistant gloves et al. These applications have created a demand for numerical modeling of the fabrics and more in depth information about the behavior of fibrous materials and yarns. Manufacturers of yams usually provide quasi-static tensile strength for the single fiber form of the material. However, this information cannot be scaled up directly for a yarn consisting of many fibers. Also, the strain rate at which this information is obtained is not in the same order of magnitude as the strain rates observed in ballistic applications. In this study, Kevlar 49® single yarn was tested in tension within a strain rate range of 20 to 100 s-1 using a high speed servo-hydraulic testing system. The failure behavior of test specimen was recorded by a high speed digital camera. Results were used to investigate the strain rate effect on the dynamic material properties in terms of Young's modulus, tensile strength, maximum strain and toughness. The dependence of dynamic material properties on the strain rate was discussed.