In this study, we successfully fabricated an intrinsically stretchable light‐emitting diode (LED) by using a new conjugated rod–coil block copolymer, poly[2,7‐(9,9‐dioctylfluorene)]‐block‐poly(isoprene) (PF‐b‐PI). ( PF conjugated rods and PI coils exhibited fluorescent and intrinsically stretchable properties, respectively. Copolymers with three different rod/coil ratios, namely PF18K‐b‐PI5K, PF12K‐b‐PI5K and PF12K‐b‐PI10K, were utilized for elastic LED demonstration. Notably, PF18K‐b‐PI5K and PF12K‐b‐PI5K LEDs can work under a strain of 140% because of suitable ratios of rod/coil lengths. Finally, a stretchable PF12K‐b‐PI5K LED was measured with a low voltage of 2 V and with a brightness of 70 cd m−2 at 10 V. This LED was subjected to 100 cycles of luminance–strain testing under 50% strain and it maintained a stable level of brightness. These results demonstrated that the luminescent PF12K‐b‐PI5K rod–coil block copolymers exhibit exceptional stretchability and high stability; these copolymers can be used in stretchable LEDs for a wide range of applications. © 2020 Society of Chemical Industry