In this chapter, the basics of the mechanical properties of conjugated polymers are delved into, including current design principles within the field aimed at manipulating these properties. A variety of strategies for controlling molecular characteristics are explored, such as molecular weight and regioregularity, as well as methods for integrating different elements into the polymer’s structure, which include modifications to the backbone and side chains. Going beyond modifying the polymer itself, copolymers with flexible units, as well as composites with elastomers, will also be discussed as an alternative way to engineer stretchable materials. A range of characterization techniques are also examined for both bulk materials and thin films, in addition to methods for a morphological analysis to grasp the changes at the molecular level caused by deformation. Furthermore, measurements of electrical properties will be addressed. Finally, some of the key applications of these materials are briefly discussed.