Polydiacetylenes (PDAs), a family of conjugated polymers, are very intriguing materials in several aspects. Especially, the stimulus-induced apparent blue-to-red transition of the PDAs has led to the development of a variety of PDA-based chemosensors. In the current work, we synthesized PDA monomers bearing trimethyl amine (PCDA-DMEDA) and incorporated them with Poly(ethylene oxide) (PEO) into electrospun fibers. For the first time, we successfully demonstrated that PDA-based electrospun fibers can be used for the naked-eye detection of HCl gas by simple color change (blue to red).