Wearable ion-selective potentiometric sensors have received considerable interest in enabling taste sensing in robots and for monitoring abnormal conditions, such as poor water quality, spoiled food (freshness), and microbial contamination. Despite advances in wearable ion-selective sensors, the production of a stretchable and miniaturized ion-selective sensor to detect various ions remains a challenge for practical applications. Herein, a stretchable multi-ply potentiometric sensor is reported based on ion-selective coiled yarn (ISCY) with Carbon nanotube. Three types of ISCYs show high sensitivity and selectivity toward a specific target ion, such as K+, Na+, and H+. The sensitivity and selectivity are maintained even at 27% strain and under mechanical deformation, such as being bent by 180° or tied into a knot. Furthermore, an attempt is made to miniaturize the sensor into a single fiber by plying three types of ISCYs and a reference electrode together. This multi-ion potentiometric sensor is successfully woven into fabrics, such as clothes or gloves, and exhibits a functional sensing performance in various water-based solutions (sea, river, tap, and distilled waters) and fruit juices as practical applications. These results suggest that this potentiometric sensor has a high potential application as a taste sensor and a monitoring sensor in an electronic tongue.