This chapter provides a broad understanding of the mechanical properties of polymers, beginning with the deformation modes and progressing through static and dynamic testing procedures. The properties, including Modulus, Stiffness, Toughness, Resilience, Hysteresis, Impact resistance, and Hardness, are discussed, followed by an in-depth depiction of failure mechanisms, abrasion resistance, and thermal effects. Finally, an in-depth analysis of stress-strain curves of different polymers, distinguishing between rubbers, plastics, and fibres, while examining the influence of fillers.