AbstractTextile sensors are crucial unobtrusive devices attached to arbitrarily curved surfaces owing to their high flexibility and ease of processing in large areas with complex contours. However, issues regarding the reliability and stability of the output of textile sensors and their practical implementation persist. This study proposes sensor yarns comprising carbon‐coated multifibers covering metallic core yarns to detect pressure and strain. Two electrically independent metallic core fibers are twisted in close proximity in a core‐sheath structure with a sheath yarn of carbon‐coated fibers. When an external force is applied, the covering yarns deform elastically, causing a change in resistance. The proposed sensor yarns can be used to develop customized textile sensors, as they can be woven or knitted at the target positions owing to their flexibility. Fabrics and knits with embedded sensor yarns can detect external forces and biological motions, e.g., respiratory monitoring and finger movements. The proposed sensors can be made sensitive or insensitive to moisture depending on the choice of the covering yarn. Thus, the proposed yarns and textile sensors have potential applications in wearable devices and biological sensors that require high conformability to the human body and curved surfaces.