One-dimensional organic nanomaterials with a combination of electric conductivity, flexibility, and mechanical robustness are highly in demand in a variety of flexible electronic devices. Herein, conducting polymers were combined with robust Kevlar nanofibrils (aramid nanofibrils, abbreviated as ANFs) via in situ polymerization. Owing to the strong interactions between ANFs and conjugated polymers, the resultant core-shell ANFs showed high electric conductivity in combination with flexibility, robustness, physical stability, and endurance to bending and solvents, in sharp contrast to many inorganic conductive nanomaterials. Due to their responsivity of conductivity to different stimuli (e.g., humidity and strain), their membranes were capable not only of sensing human motions and speech words, but also of showing high sensitivity to variation of environmental humidity. In such a way, these core -shell ANFs may pave the way for combining both conductivity and mechanical properties applicable for diverse wearable devices.