An easy and novel synthetic concept for building intrinsically stretchable and elastic semiconducting polymers is designed in this study, in which a conjugated rod-coil block copolymer with a rigid poly(9,9-di-n-octyl-2,7-fluorene) (PFO)-conjugated rod and soft poly(isoprene) (PI) coils were utilized as model compounds for demonstration. By combining a coupling reaction for a conjugated block and reversible addition-fragmentation chain transfer for a functional soft block, a simplified synthetic procedure for semiconducting polymers incorporating different lengths of the PI moiety, PF-b-(PI)(x) (x = 0.9, 1.2, and 1.8), was thus developed. Upon intense mechanical stress, both their stretching and rubbery properties associated with highly stable luminescence were demonstrated because of the molecular-level rigid island structure of self-assembly nanostructured PF domains bridged by PI segments. In particular, the PF-b-PI1.8 thin film could not only be stretched by up to 150% without forming any cracks but also be employed for the fabrication of free-standing films with both excellent elasticity and tough mechanical strength after cross-linking, showing high stability in quantum yield over 1000 stretching cycles at 150% strain.