Flexible and multifunctional microsensors have attracted wide attention owing to their multiple-sensing functions and diverse application fields. Here, we develop a series of highly flexible, multicolored, and multifunctional single-fiber-based (SFB) microsensors for flexible functional electronics. The SFB microsensors are based on the ingenious combination of single ZnO-coated carbon fiber (CF), flexible indium tin oxide/poly(ethylene terephthalate) (ITO/PET) membrane, and typing paper through a facile integration method. Specifically, a series of ZnO-coated CFs are prepared by chemically and coaxially depositing ZnO nanolayers on the CF surface through the atomic layer deposition (ALD) technique. Notably, the resultant SFB microsensors exhibit vivid and tunable structural colors originating from the thin-film interference of ZnO nanolayers as well as optical anisotropy because of the distinct axisymmetric structure of the CF. Benefiting from the optoelectronic properties of the ZnO nanolayer and delicate device structure, the SFB microsensors show a high UV sensitivity (120%) and good mechanical stability at varying bending angles (0–150°) and cycles (600 cycles). Moreover, by harnessing the pyroelectric and photothermal effects, the SFB microsensors can also be utilized to detect ambient temperature changes (0–55 °C) and IR light with high linearity, relatively high sensitivity (0.74% °C–1), and good stability. Owing to these merits, such SFB microsensors are capable of monitoring mouth respiration and nose breathing, implying their applications in wearable health monitors. This work not only integrates different sensing capabilities into a flexible device with reduced complexity but also miniaturizes the size of the device dramatically, holding tremendous prospects for diverse smart microsensing applications.