As future generations of wearable electronics are expected to be directly worn, fiber-based electronics are expected to become increasingly more important in the coming years, as they can be weaved into textiles to provide higher comfort, durability, and integrated multi-functionalities. Herein, we demonstrate an intrinsically stretchable multi-functional hollow fiber capable of harvesting mechanical energy and detecting strain. For energy harvesting, we have utilized a stretchable ferroelectric layer composed of P(VDF-TrFE) in a matrix of elastomer, sandwiched between stretchable electrodes composed of multi-walled carbon nanotubes and PEDOT:PSS. We have demonstrated voltage and current generation under stretching and normal pressure, with output voltage and current as high as 1.2 V and 10 nA, respectively. Furthermore, the hollow architecture enabled the harvesting of pressure coming from internal liquid flow, adding another dimension of harvesting mechanical energy. The stretchable electrodes were used as strain sensors, which exhibited high gauge factor of 80–177 in the 0–50% strain range, along with low hysteresis and durability. These features render our multi-functional fiber highly suitable for wearable electronic applications in the near future.