High-performance wearable electronics are highly desirable for the development of body warming and human health monitoring devices. In the present study, high electrically conductive and photothermal cotton yarns (CYs) with long-term stability were prepared as wearable electronics. The process contains back-to-back decoration of the fiber surface by Ti3C2Tx (MXene) nanosheets, and the poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) composite, to form a core–shell structure (MP@CY). The addition of a small amount of PEDOT: PSS plays a dual role of protecting the MXene from oxidation and increasing the electrical conductivity. The resulting yarn exhibits excellent electrical conductivity (21.8 Ω cm-1), rapid electrothermal response, and superb photothermal conversion capability, supporting its application as an optical/electrical dual-drive heater. A three-dimensional (3D) honeycomb-like textile wearable heater based on MP@CY as weft yarn demonstrates outstanding electrical thermal properties (0–2.5 V, 30–196.8 °C) and exceptional photothermal conversion (130 mW cm-2, 64.2 °C). Using an Internet of Things (IoT) microcontroller and Espressif (ESP) electronics chip, which are combined with wireless fidelity (Wi-Fi) and smartphone, real-time visualization and precise control of the temperature interface can be achieved. Furthermore, MP@CY-based knitted sensors, obtained by hand-knitting, are utilized for monitoring human movement and health, exhibiting high sensitivity and long-term cycling stability.