The dynamic behavior of a woven fabric submitted to a ballistic impact is a complex phenomenon. The dynamic deformations of yarns over time are still unknown both from the experimental and modeling point of view. To overcome this lack of information, a sensor yarn has been developed to monitor the dynamic strain while based on the same raw material as adjacent and close yarns inside the woven structure. This PEDOT:PSS-coated sensor has been developed and characterized both in quasi-static and dynamic modes. The mechanical and electro-mechanical behaviors were characterized in a quasi-static regime and made it possible to access the gauge factor of the sensor yarn. An impact test, corresponding to the dynamic regime, has been performed and has proven the ability of the sensor yarn to detect the transmitted dynamic waves of elongation through the fabric.