Polymer-based composites are widely used in the automotive, security, aeronautical and space industries, to mention a few. This is because of their good mechanical properties, which are similar to those of metals but with the attraction of being lightweight. Kevlar® is extensively used as a reinforcement in the security industry owing to its good ballistic properties. This investigation presents a mechanical characterization based on in-plane quasi-static tensile testing of Kevlar® 29/phenolic resin with a polyvinyl butyral composite using a universal testing system. The methodology developed for the preparation of the coupons is based on pressure, temperature and time. As a result of this work, elastic moduli (EL and ET), Poisson’s ratio (νLT), shear modulus (GLT) and strengths (XT, YT, S) were obtained. It is worth mentioning that there is scarce or no characterization of this material in the literature, and those studies that do characterize it do not present the coupons’ thermoforming conditions or the reasons for the coupons’ dimensions (width, length and thickness).