Recently, high-performance energy storage devices are urgently needed due to the rapid development of miniaturized, portable and wearable electronic equipment. However, most of the single-cell energy storage devices suffer from a relatively low operating voltage. In this work, we present a novel fiber-based micro-asymmetric supercapacitor (ASC) with high performance and good integration ability. A carbon nanoparticle coated carbon fiber (CF@CNPs) is chosen as the substrate owing to its notable features such as high porosity, high flexibility, lightweight, simple processing and ease of integration. A manganese oxide nanosheet grown on CF@CNPs and functionalized CF@CNPs are employed as the positive and negative electrode of the micro-ASC, respectively. The as-prepared ASC device can operate at 1.8 V and exhibit a high volumetric energy density of 2.1 mW h cm⁻³, which is comparable to that of a thin-film Li-battery. Furthermore, the micro-ASC can achieve a very high capacitance retention of about 82.7% when the charge and discharge current density is changed from 0.25 A cm⁻³ to 6.3 A cm⁻³, demonstrating the excellent rate capability of the ASC. The ASC also shows good cycling stability and has great potential for integration with energy harvesting devices to realize highly efficient self-powered systems.