The energy generated by the impact of vibrations from industrial tools or ongoing activities can be transmitted to humans and cause various injuries. Knitted materials can be considered as parts of anti-vibration equipment as they have proven their ability to absorb shocks. In this study, six spacer knitted fabrics consisting of two outer layers of cotton yarns (Nm 1/50 and Nm 1/40) and cashmere yarns (Nm 2/56) connected by PES monofilaments with a diameter of 0.08 mm were tested. To date, the use of natural yarns in the outer layers of spacer fabrics used in environments subject to vibration has been less studied. The first part of the experiments deals with the measurement of the natural frequencies of the materials, which were determined using the free vibration method. The results show that the direction of the experiment, the yarn count, the stitch density, and the thickness of the material influence the value of the natural frequencies. These values are relevant in order to avoid undesirable resonances that occur when the excitation frequency of an external system overlaps with the natural frequency of the material. In the second part, the vibration transmissibility was simulated using a vibration system with one degree of freedom. The fabrics composed of cotton yarns Nm 1/50 had the highest damping capacity and the highest specific damping coefficient and the lowest value for vibration transmission, which make them recommendable for protective materials.